Commit Graph

816 Commits

Author SHA1 Message Date
Paolo Bonzini
d96c77bd4e KVM: x86: switch hugepage recovery thread to vhost_task
kvm_vm_create_worker_thread() is meant to be used for kthreads that
can consume significant amounts of CPU time on behalf of a VM or in
response to how the VM behaves (for example how it accesses its memory).
Therefore it wants to charge the CPU time consumed by that work to
the VM's container.

However, because of these threads, cgroups which have kvm instances
inside never complete freezing.  This can be trivially reproduced:

  root@test ~# mkdir /sys/fs/cgroup/test
  root@test ~# echo $$ > /sys/fs/cgroup/test/cgroup.procs
  root@test ~# qemu-system-x86_64 -nographic -enable-kvm

and in another terminal:

  root@test ~# echo 1 > /sys/fs/cgroup/test/cgroup.freeze
  root@test ~# cat /sys/fs/cgroup/test/cgroup.events
  populated 1
  frozen 0

The cgroup freezing happens in the signal delivery path but
kvm_nx_huge_page_recovery_worker, while joining non-root cgroups, never
calls into the signal delivery path and thus never gets frozen. Because
the cgroup freezer determines whether a given cgroup is frozen by
comparing the number of frozen threads to the total number of threads
in the cgroup, the cgroup never becomes frozen and users waiting for
the state transition may hang indefinitely.

Since the worker kthread is tied to a user process, it's better if
it behaves similarly to user tasks as much as possible, including
being able to send SIGSTOP and SIGCONT.  In fact, vhost_task is all
that kvm_vm_create_worker_thread() wanted to be and more: not only it
inherits the userspace process's cgroups, it has other niceties like
being parented properly in the process tree.  Use it instead of the
homegrown alternative.

Incidentally, the new code is also better behaved when you flip recovery
back and forth to disabled and back to enabled.  If your recovery period
is 1 minute, it will run the next recovery after 1 minute independent
of how many times you flipped the parameter.

(Commit message based on emails from Tejun).

Reported-by: Tejun Heo <tj@kernel.org>
Reported-by: Luca Boccassi <bluca@debian.org>
Acked-by: Tejun Heo <tj@kernel.org>
Tested-by: Luca Boccassi <bluca@debian.org>
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-11-14 13:20:04 -05:00
Paolo Bonzini
0586ade9e7 LoongArch KVM changes for v6.13
1. Add iocsr and mmio bus simulation in kernel.
 2. Add in-kernel interrupt controller emulation.
 3. Add virt extension support for eiointc irqchip.
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Merge tag 'loongarch-kvm-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD

LoongArch KVM changes for v6.13

1. Add iocsr and mmio bus simulation in kernel.
2. Add in-kernel interrupt controller emulation.
3. Add virt extension support for eiointc irqchip.
2024-11-14 07:06:24 -05:00
Xianglai Li
948ccbd950 LoongArch: KVM: Add iocsr and mmio bus simulation in kernel
Add iocsr and mmio memory read and write simulation to the kernel. When
the VM accesses the device address space through iocsr instructions or
mmio, it does not need to return to the qemu user mode but can directly
completes the access in the kernel mode.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
2024-11-13 16:18:26 +08:00
Sean Christopherson
3e7f43188e KVM: Protect vCPU's "last run PID" with rwlock, not RCU
To avoid jitter on KVM_RUN due to synchronize_rcu(), use a rwlock instead
of RCU to protect vcpu->pid, a.k.a. the pid of the task last used to a
vCPU.  When userspace is doing M:N scheduling of tasks to vCPUs, e.g. to
run SEV migration helper vCPUs during post-copy, the synchronize_rcu()
needed to change the PID associated with the vCPU can stall for hundreds
of milliseconds, which is problematic for latency sensitive post-copy
operations.

In the directed yield path, do not acquire the lock if it's contended,
i.e. if the associated PID is changing, as that means the vCPU's task is
already running.

Reported-by: Steve Rutherford <srutherford@google.com>
Reviewed-by: Steve Rutherford <srutherford@google.com>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240802200136.329973-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-10-30 14:41:22 -07:00
Sean Christopherson
8b15c3764c KVM: Don't grab reference on VM_MIXEDMAP pfns that have a "struct page"
Now that KVM no longer relies on an ugly heuristic to find its struct page
references, i.e. now that KVM can't get false positives on VM_MIXEDMAP
pfns, remove KVM's hack to elevate the refcount for pfns that happen to
have a valid struct page.  In addition to removing a long-standing wart
in KVM, this allows KVM to map non-refcounted struct page memory into the
guest, e.g. for exposing GPU TTM buffers to KVM guests.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-86-seanjc@google.com>
2024-10-25 13:01:35 -04:00
Sean Christopherson
93b7da404f KVM: Drop APIs that manipulate "struct page" via pfns
Remove all kvm_{release,set}_pfn_*() APIs now that all users are gone.

No functional change intended.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-85-seanjc@google.com>
2024-10-25 13:01:35 -04:00
Sean Christopherson
06cdaff80e KVM: Drop gfn_to_pfn() APIs now that all users are gone
Drop gfn_to_pfn() and all its variants now that all users are gone.

No functional change intended.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-80-seanjc@google.com>
2024-10-25 13:01:35 -04:00
Sean Christopherson
f42e289a20 KVM: Add support for read-only usage of gfn_to_page()
Rework gfn_to_page() to support read-only accesses so that it can be used
by arm64 to get MTE tags out of guest memory.

Opportunistically rewrite the comment to be even more stern about using
gfn_to_page(), as there are very few scenarios where requiring a struct
page is actually the right thing to do (though there are such scenarios).
Add a FIXME to call out that KVM probably should be pinning pages, not
just getting pages.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-77-seanjc@google.com>
2024-10-25 13:00:50 -04:00
Sean Christopherson
dc06193532 KVM: Move x86's API to release a faultin page to common KVM
Move KVM x86's helper that "finishes" the faultin process to common KVM
so that the logic can be shared across all architectures.  Note, not all
architectures implement a fast page fault path, but the gist of the
comment applies to all architectures.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-50-seanjc@google.com>
2024-10-25 13:00:47 -04:00
Sean Christopherson
1fbee5b01a KVM: guest_memfd: Provide "struct page" as output from kvm_gmem_get_pfn()
Provide the "struct page" associated with a guest_memfd pfn as an output
from __kvm_gmem_get_pfn() so that KVM guest page fault handlers can
directly put the page instead of having to rely on
kvm_pfn_to_refcounted_page().

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-47-seanjc@google.com>
2024-10-25 13:00:47 -04:00
Sean Christopherson
1c7b627e93 KVM: Add kvm_faultin_pfn() to specifically service guest page faults
Add a new dedicated API, kvm_faultin_pfn(), for servicing guest page
faults, i.e. for getting pages/pfns that will be mapped into the guest via
an mmu_notifier-protected KVM MMU.  Keep struct kvm_follow_pfn buried in
internal code, as having __kvm_faultin_pfn() take "out" params is actually
cleaner for several architectures, e.g. it allows the caller to have its
own "page fault" structure without having to marshal data to/from
kvm_follow_pfn.

Long term, common KVM would ideally provide a kvm_page_fault structure, a
la x86's struct of the same name.  But all architectures need to be
converted to a common API before that can happen.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-44-seanjc@google.com>
2024-10-25 13:00:47 -04:00
Sean Christopherson
21dd877060 KVM: Move declarations of memslot accessors up in kvm_host.h
Move the memslot lookup helpers further up in kvm_host.h so that they can
be used by inlined "to pfn" wrappers.

No functional change intended.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-43-seanjc@google.com>
2024-10-25 13:00:07 -04:00
Sean Christopherson
365e319208 KVM: Pass in write/dirty to kvm_vcpu_map(), not kvm_vcpu_unmap()
Now that all kvm_vcpu_{,un}map() users pass "true" for @dirty, have them
pass "true" as a @writable param to kvm_vcpu_map(), and thus create a
read-only mapping when possible.

Note, creating read-only mappings can be theoretically slower, as they
don't play nice with fast GUP due to the need to break CoW before mapping
the underlying PFN.  But practically speaking, creating a mapping isn't
a super hot path, and getting a writable mapping for reading is weird and
confusing.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-34-seanjc@google.com>
2024-10-25 12:59:07 -04:00
Sean Christopherson
2bcb52a360 KVM: Pin (as in FOLL_PIN) pages during kvm_vcpu_map()
Pin, as in FOLL_PIN, pages when mapping them for direct access by KVM.
As per Documentation/core-api/pin_user_pages.rst, writing to a page that
was gotten via FOLL_GET is explicitly disallowed.

  Correct (uses FOLL_PIN calls):
      pin_user_pages()
      write to the data within the pages
      unpin_user_pages()

  INCORRECT (uses FOLL_GET calls):
      get_user_pages()
      write to the data within the pages
      put_page()

Unfortunately, FOLL_PIN is a "private" flag, and so kvm_follow_pfn must
use a one-off bool instead of being able to piggyback the "flags" field.

Link: https://lwn.net/Articles/930667
Link: https://lore.kernel.org/all/cover.1683044162.git.lstoakes@gmail.com
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-32-seanjc@google.com>
2024-10-25 12:58:00 -04:00
David Stevens
2ff072ba7a KVM: Migrate kvm_vcpu_map() to kvm_follow_pfn()
Migrate kvm_vcpu_map() to kvm_follow_pfn(), and have it track whether or
not the map holds a refcounted struct page.  Precisely tracking struct
page references will eventually allow removing kvm_pfn_to_refcounted_page()
and its various wrappers.

Signed-off-by: David Stevens <stevensd@chromium.org>
[sean: use a pointer instead of a boolean]
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-31-seanjc@google.com>
2024-10-25 12:57:59 -04:00
Sean Christopherson
ef7db98e47 KVM: Use NULL for struct page pointer to indicate mremapped memory
Drop yet another unnecessary magic page value from KVM, as there's zero
reason to use a poisoned pointer to indicate "no page".  If KVM uses a
NULL page pointer, the kernel will explode just as quickly as if KVM uses
a poisoned pointer.  Never mind the fact that such usage would be a
blatant and egregious KVM bug.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-23-seanjc@google.com>
2024-10-25 12:57:59 -04:00
Sean Christopherson
cccefb0a0d KVM: Drop unused "hva" pointer from __gfn_to_pfn_memslot()
Drop @hva from __gfn_to_pfn_memslot() now that all callers pass NULL.

No functional change intended.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-19-seanjc@google.com>
2024-10-25 12:57:58 -04:00
David Stevens
6769d1bcd3 KVM: Replace "async" pointer in gfn=>pfn with "no_wait" and error code
Add a pfn error code to communicate that hva_to_pfn() failed because I/O
was needed and disallowed, and convert @async to a constant @no_wait
boolean.  This will allow eliminating the @no_wait param by having callers
pass in FOLL_NOWAIT along with other FOLL_* flags.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: David Stevens <stevensd@chromium.org>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-17-seanjc@google.com>
2024-10-25 12:57:58 -04:00
Sean Christopherson
e2d2ca71ac KVM: Drop @atomic param from gfn=>pfn and hva=>pfn APIs
Drop @atomic from the myriad "to_pfn" APIs now that all callers pass
"false", and remove a comment blurb about KVM running only the "GUP fast"
part in atomic context.

No functional change intended.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-13-seanjc@google.com>
2024-10-25 12:57:58 -04:00
Sean Christopherson
6419bc5207 KVM: Rename gfn_to_page_many_atomic() to kvm_prefetch_pages()
Rename gfn_to_page_many_atomic() to kvm_prefetch_pages() to try and
communicate its true purpose, as the "atomic" aspect is essentially a
side effect of the fact that x86 uses the API while holding mmu_lock.
E.g. even if mmu_lock weren't held, KVM wouldn't want to fault-in pages,
as the goal is to opportunistically grab surrounding pages that have
already been accessed and/or dirtied by the host, and to do so quickly.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-12-seanjc@google.com>
2024-10-25 12:55:12 -04:00
Sean Christopherson
3af91068b7 KVM: Add kvm_release_page_unused() API to put pages that KVM never consumes
Add an API to release an unused page, i.e. to put a page without marking
it accessed or dirty.  The API will be used when KVM faults-in a page but
bails before installing the guest mapping (and other similar flows).

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-4-seanjc@google.com>
2024-10-25 12:54:42 -04:00
Sean Christopherson
037bc38b29 KVM: Drop KVM_ERR_PTR_BAD_PAGE and instead return NULL to indicate an error
Remove KVM_ERR_PTR_BAD_PAGE and instead return NULL, as "bad page" is just
a leftover bit of weirdness from days of old when KVM stuffed a "bad" page
into the guest instead of actually handling missing pages.  See commit
cea7bb2128 ("KVM: MMU: Make gfn_to_page() always safe").

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-2-seanjc@google.com>
2024-10-25 12:54:42 -04:00
Dr. David Alan Gilbert
bc07eea2f3 KVM: Remove unused kvm_vcpu_gfn_to_pfn_atomic
The last use of kvm_vcpu_gfn_to_pfn_atomic was removed by commit
1bbc60d0c7 ("KVM: x86/mmu: Remove MMU auditing")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Message-ID: <20241001141354.18009-3-linux@treblig.org>
[Adjust Documentation/virt/kvm/locking.rst. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-10-20 07:05:51 -04:00
Dr. David Alan Gilbert
88a387cf9e KVM: Remove unused kvm_vcpu_gfn_to_pfn
The last use of kvm_vcpu_gfn_to_pfn was removed by commit
b1624f99aa ("KVM: Remove kvm_vcpu_gfn_to_page() and kvm_vcpu_gpa_to_page()")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Message-ID: <20241001141354.18009-2-linux@treblig.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-10-20 07:04:52 -04:00
Paolo Bonzini
c09dd2bb57 Merge branch 'kvm-redo-enable-virt' into HEAD
Register KVM's cpuhp and syscore callbacks when enabling virtualization in
hardware, as the sole purpose of said callbacks is to disable and re-enable
virtualization as needed.

The primary motivation for this series is to simplify dealing with enabling
virtualization for Intel's TDX, which needs to enable virtualization
when kvm-intel.ko is loaded, i.e. long before the first VM is created.

That said, this is a nice cleanup on its own.  By registering the callbacks
on-demand, the callbacks themselves don't need to check kvm_usage_count,
because their very existence implies a non-zero count.

Patch 1 (re)adds a dedicated lock for kvm_usage_count.  This avoids a
lock ordering issue between cpus_read_lock() and kvm_lock.  The lock
ordering issue still exist in very rare cases, and will be fixed for
good by switching vm_list to an (S)RCU-protected list.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-09-17 11:38:20 -04:00
Sean Christopherson
b67107a251 KVM: Add arch hooks for enabling/disabling virtualization
Add arch hooks that are invoked when KVM enables/disable virtualization.
x86 will use the hooks to register an "emergency disable" callback, which
is essentially an x86-specific shutdown notifier that is used when the
kernel is doing an emergency reboot/shutdown/kexec.

Add comments for the declarations to help arch code understand exactly
when the callbacks are invoked.  Alternatively, the APIs themselves could
communicate most of the same info, but kvm_arch_pre_enable_virtualization()
and kvm_arch_post_disable_virtualization() are a bit cumbersome, and make
it a bit less obvious that they are intended to be implemented as a pair.

Reviewed-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240830043600.127750-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-09-04 11:02:33 -04:00
Sean Christopherson
071f24ad28 KVM: Rename arch hooks related to per-CPU virtualization enabling
Rename the per-CPU hooks used to enable virtualization in hardware to
align with the KVM-wide helpers in kvm_main.c, and to better capture that
the callbacks are invoked on every online CPU.

No functional change intended.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Message-ID: <20240830043600.127750-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-09-04 11:02:33 -04:00
Leonardo Bras
593377036e kvm: Note an RCU quiescent state on guest exit
As of today, KVM notes a quiescent state only in guest entry, which is good
as it avoids the guest being interrupted for current RCU operations.

While the guest vcpu runs, it can be interrupted by a timer IRQ that will
check for any RCU operations waiting for this CPU. In case there are any of
such, it invokes rcu_core() in order to sched-out the current thread and
note a quiescent state.

This occasional schedule work will introduce tens of microsseconds of
latency, which is really bad for vcpus running latency-sensitive
applications, such as real-time workloads.

So, note a quiescent state in guest exit, so the interrupted guests is able
to deal with any pending RCU operations before being required to invoke
rcu_core(), and thus avoid the overhead of related scheduler work.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240511020557.1198200-1-leobras@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-09-04 10:44:42 -04:00
Sean Christopherson
66155de93b KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX)
Disallow read-only memslots for SEV-{ES,SNP} VM types, as KVM can't
directly emulate instructions for ES/SNP, and instead the guest must
explicitly request emulation.  Unless the guest explicitly requests
emulation without accessing memory, ES/SNP relies on KVM creating an MMIO
SPTE, with the subsequent #NPF being reflected into the guest as a #VC.

But for read-only memslots, KVM deliberately doesn't create MMIO SPTEs,
because except for ES/SNP, doing so requires setting reserved bits in the
SPTE, i.e. the SPTE can't be readable while also generating a #VC on
writes.  Because KVM never creates MMIO SPTEs and jumps directly to
emulation, the guest never gets a #VC.  And since KVM simply resumes the
guest if ES/SNP guests trigger emulation, KVM effectively puts the vCPU
into an infinite #NPF loop if the vCPU attempts to write read-only memory.

Disallow read-only memory for all VMs with protected state, i.e. for
upcoming TDX VMs as well as ES/SNP VMs.  For TDX, it's actually possible
to support read-only memory, as TDX uses EPT Violation #VE to reflect the
fault into the guest, e.g. KVM could configure read-only SPTEs with RX
protections and SUPPRESS_VE=0.  But there is no strong use case for
supporting read-only memslots on TDX, e.g. the main historical usage is
to emulate option ROMs, but TDX disallows executing from shared memory.
And if someone comes along with a legitimate, strong use case, the
restriction can always be lifted for TDX.

Don't bother trying to retroactively apply the restriction to SEV-ES
VMs that are created as type KVM_X86_DEFAULT_VM.  Read-only memslots can't
possibly work for SEV-ES, i.e. disallowing such memslots is really just
means reporting an error to userspace instead of silently hanging vCPUs.
Trying to deal with the ordering between KVM_SEV_INIT and memslot creation
isn't worth the marginal benefit it would provide userspace.

Fixes: 26c44aa9e0 ("KVM: SEV: define VM types for SEV and SEV-ES")
Fixes: 1dfe571c12 ("KVM: SEV: Add initial SEV-SNP support")
Cc: Peter Gonda <pgonda@google.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Vishal Annapurve <vannapurve@google.com>
Cc: Ackerly Tng <ackerleytng@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240809190319.1710470-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-08-14 12:28:24 -04:00
Paolo Bonzini
e4ee544792 KVM: guest_memfd: let kvm_gmem_populate() operate only on private gfns
This check is currently performed by sev_gmem_post_populate(), but it
applies to all callers of kvm_gmem_populate(): the point of the function
is that the memory is being encrypted and some work has to be done
on all the gfns in order to encrypt them.

Therefore, check the KVM_MEMORY_ATTRIBUTE_PRIVATE attribute prior
to invoking the callback, and stop the operation if a shared page
is encountered.  Because CONFIG_KVM_PRIVATE_MEM in principle does
not require attributes, this makes kvm_gmem_populate() depend on
CONFIG_KVM_GENERIC_PRIVATE_MEM (which does require them).

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-07-26 14:46:15 -04:00
Paolo Bonzini
4b5f67120a KVM: extend kvm_range_has_memory_attributes() to check subset of attributes
While currently there is no other attribute than KVM_MEMORY_ATTRIBUTE_PRIVATE,
KVM code such as kvm_mem_is_private() is written to expect their existence.
Allow using kvm_range_has_memory_attributes() as a multi-page version of
kvm_mem_is_private(), without it breaking later when more attributes are
introduced.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-07-26 14:46:15 -04:00
Paolo Bonzini
7239ed7467 KVM: remove kvm_arch_gmem_prepare_needed()
It is enough to return 0 if a guest need not do any preparation.
This is in fact how sev_gmem_prepare() works for non-SNP guests,
and it extends naturally to Intel hosts: the x86 callback for
gmem_prepare is optional and returns 0 if not defined.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-07-26 14:46:14 -04:00
Paolo Bonzini
564429a6bd KVM: rename CONFIG_HAVE_KVM_GMEM_* to CONFIG_HAVE_KVM_ARCH_GMEM_*
Add "ARCH" to the symbols; shortly, the "prepare" phase will include both
the arch-independent step to clear out contents left in the page by the
host, and the arch-dependent step enabled by CONFIG_HAVE_KVM_GMEM_PREPARE.
For consistency do the same for CONFIG_HAVE_KVM_GMEM_INVALIDATE as well.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-07-26 14:46:14 -04:00
Paolo Bonzini
86014c1e20 KVM generic changes for 6.11
- Enable halt poll shrinking by default, as Intel found it to be a clear win.
 
  - Setup empty IRQ routing when creating a VM to avoid having to synchronize
    SRCU when creating a split IRQCHIP on x86.
 
  - Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
    that arch code can use for hooking both sched_in() and sched_out().
 
  - Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
    truncating a bogus value from userspace, e.g. to help userspace detect bugs.
 
  - Mark a vCPU as preempted if and only if it's scheduled out while in the
    KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
    memory when retrieving guest state during live migration blackout.
 
  - A few minor cleanups
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Merge tag 'kvm-x86-generic-6.11' of https://github.com/kvm-x86/linux into HEAD

KVM generic changes for 6.11

 - Enable halt poll shrinking by default, as Intel found it to be a clear win.

 - Setup empty IRQ routing when creating a VM to avoid having to synchronize
   SRCU when creating a split IRQCHIP on x86.

 - Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
   that arch code can use for hooking both sched_in() and sched_out().

 - Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
   truncating a bogus value from userspace, e.g. to help userspace detect bugs.

 - Mark a vCPU as preempted if and only if it's scheduled out while in the
   KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
   memory when retrieving guest state during live migration blackout.

 - A few minor cleanups
2024-07-16 09:51:36 -04:00
Isaku Yamahata
bc1a5cd002 KVM: Add KVM_PRE_FAULT_MEMORY vcpu ioctl to pre-populate guest memory
Add a new ioctl KVM_PRE_FAULT_MEMORY in the KVM common code. It iterates on the
memory range and calls the arch-specific function.  The implementation is
optional and enabled by a Kconfig symbol.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <819322b8f25971f2b9933bfa4506e618508ad782.1712785629.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-07-12 11:17:35 -04:00
David Matlack
a6816314af KVM: Introduce vcpu->wants_to_run
Introduce vcpu->wants_to_run to indicate when a vCPU is in its core run
loop, i.e. when the vCPU is running the KVM_RUN ioctl and immediate_exit
was not set.

Replace all references to vcpu->run->immediate_exit with
!vcpu->wants_to_run to avoid TOCTOU races with userspace. For example, a
malicious userspace could invoked KVM_RUN with immediate_exit=true and
then after KVM reads it to set wants_to_run=false, flip it to false.
This would result in the vCPU running in KVM_RUN with
wants_to_run=false. This wouldn't cause any real bugs today but is a
dangerous landmine.

Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20240503181734.1467938-2-dmatlack@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-18 09:20:01 -07:00
Sean Christopherson
2a27c43140 KVM: Delete the now unused kvm_arch_sched_in()
Delete kvm_arch_sched_in() now that all implementations are nops.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-11 14:18:45 -07:00
Sean Christopherson
d1ae567fb8 KVM: Add a flag to track if a loaded vCPU is scheduled out
Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of
being scheduled out (vCPU put path), or if the vCPU is being reloaded
after being scheduled out (vCPU load path).  In the short term, this will
allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out
during kvm_arch_vcpu_load().

Longer term, scheduled_out opens up other potential optimizations, without
creating subtle/brittle dependencies.  E.g. it allows KVM to keep guest
state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across
kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host
kernel.  Forcing arch code to coordinate between kvm_arch_sched_{in,out}()
and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the
exact ordering of calls into arch code.

Adding scheduled_out also obviates the need for a kvm_arch_sched_out()
hook, e.g. if arch code needs to do something novel when putting vCPU
state.

And even if KVM never uses scheduled_out for anything beyond dropping
kvm_arch_sched_in(), just being able to remove all of the arch stubs makes
it worth adding the flag.

Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com
Cc: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-11 14:18:42 -07:00
Yi Wang
fbe4a7e881 KVM: Setup empty IRQ routing when creating a VM
Setup empty IRQ routing during VM creation so that x86 and s390 don't need
to set empty/dummy IRQ routing during KVM_CREATE_IRQCHIP (in future
patches).  Initializing IRQ routing before there are any potential readers
allows KVM to avoid the synchronize_srcu() in kvm_set_irq_routing(), which
can introduces 20+ milliseconds of latency in the VM creation path.

Ensuring that all VMs have non-NULL IRQ routing also hardens KVM against
misbehaving userspace VMMs, e.g. RISC-V dynamically instantiates its
interrupt controller, but doesn't override kvm_arch_intc_initialized() or
kvm_arch_irqfd_allowed(), and so can likely reach kvm_irq_map_gsi()
without fully initialized IRQ routing.

Signed-off-by: Yi Wang <foxywang@tencent.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20240506101751.3145407-2-foxywang@tencent.com
[sean: init refcount after IRQ routing, fix stub, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-11 14:18:34 -07:00
Borislav Petkov
96a02b9fa9 KVM: Unexport kvm_debugfs_dir
After

  faf01aef05 ("KVM: PPC: Merge powerpc's debugfs entry content into generic entry")

kvm_debugfs_dir is not used anywhere else outside of kvm_main.c

Unexport it and make it static.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240515150804.9354-1-bp@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-03 08:22:59 -07:00
Paolo Bonzini
7323260373 Merge branch 'kvm-coco-hooks' into HEAD
Common patches for the target-independent functionality and hooks
that are needed by SEV-SNP and TDX.
2024-05-12 04:07:01 -04:00
Paolo Bonzini
f4bc1373d5 KVM cleanups for 6.10:
- Misc cleanups extracted from the "exit on missing userspace mapping" series,
    which has been put on hold in anticipation of a "KVM Userfault" approach,
    which should provide a superset of functionality.
 
  - Remove kvm_make_all_cpus_request_except(), which got added to hack around an
    AVIC bug, and then became dead code when a more robust fix came along.
 
  - Fix a goof in the KVM_CREATE_GUEST_MEMFD documentation.
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Merge tag 'kvm-x86-generic-6.10' of https://github.com/kvm-x86/linux into HEAD

KVM cleanups for 6.10:

 - Misc cleanups extracted from the "exit on missing userspace mapping" series,
   which has been put on hold in anticipation of a "KVM Userfault" approach,
   which should provide a superset of functionality.

 - Remove kvm_make_all_cpus_request_except(), which got added to hack around an
   AVIC bug, and then became dead code when a more robust fix came along.

 - Fix a goof in the KVM_CREATE_GUEST_MEMFD documentation.
2024-05-12 03:16:47 -04:00
Michael Roth
a90764f0e4 KVM: guest_memfd: Add hook for invalidating memory
In some cases, like with SEV-SNP, guest memory needs to be updated in a
platform-specific manner before it can be safely freed back to the host.
Wire up arch-defined hooks to the .free_folio kvm_gmem_aops callback to
allow for special handling of this sort when freeing memory in response
to FALLOC_FL_PUNCH_HOLE operations and when releasing the inode, and go
ahead and define an arch-specific hook for x86 since it will be needed
for handling memory used for SEV-SNP guests.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20231230172351.574091-6-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-05-10 13:11:48 -04:00
Paolo Bonzini
1f6c06b177 KVM: guest_memfd: Add interface for populating gmem pages with user data
During guest run-time, kvm_arch_gmem_prepare() is issued as needed to
prepare newly-allocated gmem pages prior to mapping them into the guest.
In the case of SEV-SNP, this mainly involves setting the pages to
private in the RMP table.

However, for the GPA ranges comprising the initial guest payload, which
are encrypted/measured prior to starting the guest, the gmem pages need
to be accessed prior to setting them to private in the RMP table so they
can be initialized with the userspace-provided data. Additionally, an
SNP firmware call is needed afterward to encrypt them in-place and
measure the contents into the guest's launch digest.

While it is possible to bypass the kvm_arch_gmem_prepare() hooks so that
this handling can be done in an open-coded/vendor-specific manner, this
may expose more gmem-internal state/dependencies to external callers
than necessary. Try to avoid this by implementing an interface that
tries to handle as much of the common functionality inside gmem as
possible, while also making it generic enough to potentially be
usable/extensible for TDX as well.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-05-10 13:11:47 -04:00
Paolo Bonzini
3bb2531e20 KVM: guest_memfd: Add hook for initializing memory
guest_memfd pages are generally expected to be in some arch-defined
initial state prior to using them for guest memory. For SEV-SNP this
initial state is 'private', or 'guest-owned', and requires additional
operations to move these pages into a 'private' state by updating the
corresponding entries the RMP table.

Allow for an arch-defined hook to handle updates of this sort, and go
ahead and implement one for x86 so KVM implementations like AMD SVM can
register a kvm_x86_ops callback to handle these updates for SEV-SNP
guests.

The preparation callback is always called when allocating/grabbing
folios via gmem, and it is up to the architecture to keep track of
whether or not the pages are already in the expected state (e.g. the RMP
table in the case of SEV-SNP).

In some cases, it is necessary to defer the preparation of the pages to
handle things like in-place encryption of initial guest memory payloads
before marking these pages as 'private'/'guest-owned'.  Add an argument
(always true for now) to kvm_gmem_get_folio() that allows for the
preparation callback to be bypassed.  To detect possible issues in
the way userspace initializes memory, it is only possible to add an
unprepared page if it is not already included in the filemap.

Link: https://lore.kernel.org/lkml/ZLqVdvsF11Ddo7Dq@google.com/
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20231230172351.574091-5-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-05-10 13:11:46 -04:00
Venkatesh Srinivas
82e9c84d87 KVM: Remove kvm_make_all_cpus_request_except()
Remove kvm_make_all_cpus_request_except() as it effectively has no users,
and arguably should never have been added in the first place.

Commit 54163a346d ("KVM: Introduce kvm_make_all_cpus_request_except()")
added the "except" variation for use in SVM's AVIC update path, which used
it to skip sending a request to the current vCPU (commit 7d611233b0
("KVM: SVM: Disable AVIC before setting V_IRQ")).

But the AVIC usage of kvm_make_all_cpus_request_except() was essentially a
hack-a-fix that simply squashed the most likely scenario of a racy WARN
without addressing the underlying problem(s).  Commit f1577ab214 ("KVM:
SVM: svm_set_vintr don't warn if AVIC is active but is about to be
deactivated") eventually fixed the WARN itself, and the "except" usage was
subsequently dropped by df63202fe5 ("KVM: x86: APICv: drop immediate
APICv disablement on current vCPU").

That kvm_make_all_cpus_request_except() hasn't gained any users in the
last ~3 years isn't a coincidence.  If a VM-wide broadcast *needs* to skip
the current vCPU, then odds are very good that there is underlying bug
that could be better fixed elsewhere.

Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org>
Link: https://lore.kernel.org/r/20240404232651.1645176-1-venkateshs@chromium.org
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-05-02 07:47:03 -07:00
Paolo Bonzini
f3b65bbaed KVM: delete .change_pte MMU notifier callback
The .change_pte() MMU notifier callback was intended as an
optimization. The original point of it was that KSM could tell KVM to flip
its secondary PTE to a new location without having to first zap it. At
the time there was also an .invalidate_page() callback; both of them were
*not* bracketed by calls to mmu_notifier_invalidate_range_{start,end}(),
and .invalidate_page() also doubled as a fallback implementation of
.change_pte().

Later on, however, both callbacks were changed to occur within an
invalidate_range_start/end() block.

In the case of .change_pte(), commit 6bdb913f0a ("mm: wrap calls to
set_pte_at_notify with invalidate_range_start and invalidate_range_end",
2012-10-09) did so to remove the fallback from .invalidate_page() to
.change_pte() and allow sleepable .invalidate_page() hooks.

This however made KVM's usage of the .change_pte() callback completely
moot, because KVM unmaps the sPTEs during .invalidate_range_start()
and therefore .change_pte() has no hope of finding a sPTE to change.
Drop the generic KVM code that dispatches to kvm_set_spte_gfn(), as
well as all the architecture specific implementations.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Anup Patel <anup@brainfault.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Message-ID: <20240405115815.3226315-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-04-11 13:18:27 -04:00
Linus Torvalds
4f712ee0cb S390:
* Changes to FPU handling came in via the main s390 pull request
 
 * Only deliver to the guest the SCLP events that userspace has
   requested.
 
 * More virtual vs physical address fixes (only a cleanup since
   virtual and physical address spaces are currently the same).
 
 * Fix selftests undefined behavior.
 
 x86:
 
 * Fix a restriction that the guest can't program a PMU event whose
   encoding matches an architectural event that isn't included in the
   guest CPUID.  The enumeration of an architectural event only says
   that if a CPU supports an architectural event, then the event can be
   programmed *using the architectural encoding*.  The enumeration does
   NOT say anything about the encoding when the CPU doesn't report support
   the event *in general*.  It might support it, and it might support it
   using the same encoding that made it into the architectural PMU spec.
 
 * Fix a variety of bugs in KVM's emulation of RDPMC (more details on
   individual commits) and add a selftest to verify KVM correctly emulates
   RDMPC, counter availability, and a variety of other PMC-related
   behaviors that depend on guest CPUID and therefore are easier to
   validate with selftests than with custom guests (aka kvm-unit-tests).
 
 * Zero out PMU state on AMD if the virtual PMU is disabled, it does not
   cause any bug but it wastes time in various cases where KVM would check
   if a PMC event needs to be synthesized.
 
 * Optimize triggering of emulated events, with a nice ~10% performance
   improvement in VM-Exit microbenchmarks when a vPMU is exposed to the
   guest.
 
 * Tighten the check for "PMI in guest" to reduce false positives if an NMI
   arrives in the host while KVM is handling an IRQ VM-Exit.
 
 * Fix a bug where KVM would report stale/bogus exit qualification information
   when exiting to userspace with an internal error exit code.
 
 * Add a VMX flag in /proc/cpuinfo to report 5-level EPT support.
 
 * Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
   read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
 
 * Tear down TDP MMU page tables at 4KiB granularity (used to be 1GiB).  KVM
   doesn't support yielding in the middle of processing a zap, and 1GiB
   granularity resulted in multi-millisecond lags that are quite impolite
   for CONFIG_PREEMPT kernels.
 
 * Allocate write-tracking metadata on-demand to avoid the memory overhead when
   a kernel is built with i915 virtualization support but the workloads use
   neither shadow paging nor i915 virtualization.
 
 * Explicitly initialize a variety of on-stack variables in the emulator that
   triggered KMSAN false positives.
 
 * Fix the debugregs ABI for 32-bit KVM.
 
 * Rework the "force immediate exit" code so that vendor code ultimately decides
   how and when to force the exit, which allowed some optimization for both
   Intel and AMD.
 
 * Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
   vCPU creation ultimately failed, causing extra unnecessary work.
 
 * Cleanup the logic for checking if the currently loaded vCPU is in-kernel.
 
 * Harden against underflowing the active mmu_notifier invalidation
   count, so that "bad" invalidations (usually due to bugs elsehwere in the
   kernel) are detected earlier and are less likely to hang the kernel.
 
 x86 Xen emulation:
 
 * Overlay pages can now be cached based on host virtual address,
   instead of guest physical addresses.  This removes the need to
   reconfigure and invalidate the cache if the guest changes the
   gpa but the underlying host virtual address remains the same.
 
 * When possible, use a single host TSC value when computing the deadline for
   Xen timers in order to improve the accuracy of the timer emulation.
 
 * Inject pending upcall events when the vCPU software-enables its APIC to fix
   a bug where an upcall can be lost (and to follow Xen's behavior).
 
 * Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
   events fails, e.g. if the guest has aliased xAPIC IDs.
 
 RISC-V:
 
 * Support exception and interrupt handling in selftests
 
 * New self test for RISC-V architectural timer (Sstc extension)
 
 * New extension support (Ztso, Zacas)
 
 * Support userspace emulation of random number seed CSRs.
 
 ARM:
 
 * Infrastructure for building KVM's trap configuration based on the
   architectural features (or lack thereof) advertised in the VM's ID
   registers
 
 * Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
   x86's WC) at stage-2, improving the performance of interacting with
   assigned devices that can tolerate it
 
 * Conversion of KVM's representation of LPIs to an xarray, utilized to
   address serialization some of the serialization on the LPI injection
   path
 
 * Support for _architectural_ VHE-only systems, advertised through the
   absence of FEAT_E2H0 in the CPU's ID register
 
 * Miscellaneous cleanups, fixes, and spelling corrections to KVM and
   selftests
 
 LoongArch:
 
 * Set reserved bits as zero in CPUCFG.
 
 * Start SW timer only when vcpu is blocking.
 
 * Do not restart SW timer when it is expired.
 
 * Remove unnecessary CSR register saving during enter guest.
 
 * Misc cleanups and fixes as usual.
 
 Generic:
 
 * cleanup Kconfig by removing CONFIG_HAVE_KVM, which was basically always
   true on all architectures except MIPS (where Kconfig determines the
   available depending on CPU capabilities).  It is replaced either by
   an architecture-dependent symbol for MIPS, and IS_ENABLED(CONFIG_KVM)
   everywhere else.
 
 * Factor common "select" statements in common code instead of requiring
   each architecture to specify it
 
 * Remove thoroughly obsolete APIs from the uapi headers.
 
 * Move architecture-dependent stuff to uapi/asm/kvm.h
 
 * Always flush the async page fault workqueue when a work item is being
   removed, especially during vCPU destruction, to ensure that there are no
   workers running in KVM code when all references to KVM-the-module are gone,
   i.e. to prevent a very unlikely use-after-free if kvm.ko is unloaded.
 
 * Grab a reference to the VM's mm_struct in the async #PF worker itself instead
   of gifting the worker a reference, so that there's no need to remember
   to *conditionally* clean up after the worker.
 
 Selftests:
 
 * Reduce boilerplate especially when utilize selftest TAP infrastructure.
 
 * Add basic smoke tests for SEV and SEV-ES, along with a pile of library
   support for handling private/encrypted/protected memory.
 
 * Fix benign bugs where tests neglect to close() guest_memfd files.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm updates from Paolo Bonzini:
 "S390:

   - Changes to FPU handling came in via the main s390 pull request

   - Only deliver to the guest the SCLP events that userspace has
     requested

   - More virtual vs physical address fixes (only a cleanup since
     virtual and physical address spaces are currently the same)

   - Fix selftests undefined behavior

  x86:

   - Fix a restriction that the guest can't program a PMU event whose
     encoding matches an architectural event that isn't included in the
     guest CPUID. The enumeration of an architectural event only says
     that if a CPU supports an architectural event, then the event can
     be programmed *using the architectural encoding*. The enumeration
     does NOT say anything about the encoding when the CPU doesn't
     report support the event *in general*. It might support it, and it
     might support it using the same encoding that made it into the
     architectural PMU spec

   - Fix a variety of bugs in KVM's emulation of RDPMC (more details on
     individual commits) and add a selftest to verify KVM correctly
     emulates RDMPC, counter availability, and a variety of other
     PMC-related behaviors that depend on guest CPUID and therefore are
     easier to validate with selftests than with custom guests (aka
     kvm-unit-tests)

   - Zero out PMU state on AMD if the virtual PMU is disabled, it does
     not cause any bug but it wastes time in various cases where KVM
     would check if a PMC event needs to be synthesized

   - Optimize triggering of emulated events, with a nice ~10%
     performance improvement in VM-Exit microbenchmarks when a vPMU is
     exposed to the guest

   - Tighten the check for "PMI in guest" to reduce false positives if
     an NMI arrives in the host while KVM is handling an IRQ VM-Exit

   - Fix a bug where KVM would report stale/bogus exit qualification
     information when exiting to userspace with an internal error exit
     code

   - Add a VMX flag in /proc/cpuinfo to report 5-level EPT support

   - Rework TDP MMU root unload, free, and alloc to run with mmu_lock
     held for read, e.g. to avoid serializing vCPUs when userspace
     deletes a memslot

   - Tear down TDP MMU page tables at 4KiB granularity (used to be
     1GiB). KVM doesn't support yielding in the middle of processing a
     zap, and 1GiB granularity resulted in multi-millisecond lags that
     are quite impolite for CONFIG_PREEMPT kernels

   - Allocate write-tracking metadata on-demand to avoid the memory
     overhead when a kernel is built with i915 virtualization support
     but the workloads use neither shadow paging nor i915 virtualization

   - Explicitly initialize a variety of on-stack variables in the
     emulator that triggered KMSAN false positives

   - Fix the debugregs ABI for 32-bit KVM

   - Rework the "force immediate exit" code so that vendor code
     ultimately decides how and when to force the exit, which allowed
     some optimization for both Intel and AMD

   - Fix a long-standing bug where kvm_has_noapic_vcpu could be left
     elevated if vCPU creation ultimately failed, causing extra
     unnecessary work

   - Cleanup the logic for checking if the currently loaded vCPU is
     in-kernel

   - Harden against underflowing the active mmu_notifier invalidation
     count, so that "bad" invalidations (usually due to bugs elsehwere
     in the kernel) are detected earlier and are less likely to hang the
     kernel

  x86 Xen emulation:

   - Overlay pages can now be cached based on host virtual address,
     instead of guest physical addresses. This removes the need to
     reconfigure and invalidate the cache if the guest changes the gpa
     but the underlying host virtual address remains the same

   - When possible, use a single host TSC value when computing the
     deadline for Xen timers in order to improve the accuracy of the
     timer emulation

   - Inject pending upcall events when the vCPU software-enables its
     APIC to fix a bug where an upcall can be lost (and to follow Xen's
     behavior)

   - Fall back to the slow path instead of warning if "fast" IRQ
     delivery of Xen events fails, e.g. if the guest has aliased xAPIC
     IDs

  RISC-V:

   - Support exception and interrupt handling in selftests

   - New self test for RISC-V architectural timer (Sstc extension)

   - New extension support (Ztso, Zacas)

   - Support userspace emulation of random number seed CSRs

  ARM:

   - Infrastructure for building KVM's trap configuration based on the
     architectural features (or lack thereof) advertised in the VM's ID
     registers

   - Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
     x86's WC) at stage-2, improving the performance of interacting with
     assigned devices that can tolerate it

   - Conversion of KVM's representation of LPIs to an xarray, utilized
     to address serialization some of the serialization on the LPI
     injection path

   - Support for _architectural_ VHE-only systems, advertised through
     the absence of FEAT_E2H0 in the CPU's ID register

   - Miscellaneous cleanups, fixes, and spelling corrections to KVM and
     selftests

  LoongArch:

   - Set reserved bits as zero in CPUCFG

   - Start SW timer only when vcpu is blocking

   - Do not restart SW timer when it is expired

   - Remove unnecessary CSR register saving during enter guest

   - Misc cleanups and fixes as usual

  Generic:

   - Clean up Kconfig by removing CONFIG_HAVE_KVM, which was basically
     always true on all architectures except MIPS (where Kconfig
     determines the available depending on CPU capabilities). It is
     replaced either by an architecture-dependent symbol for MIPS, and
     IS_ENABLED(CONFIG_KVM) everywhere else

   - Factor common "select" statements in common code instead of
     requiring each architecture to specify it

   - Remove thoroughly obsolete APIs from the uapi headers

   - Move architecture-dependent stuff to uapi/asm/kvm.h

   - Always flush the async page fault workqueue when a work item is
     being removed, especially during vCPU destruction, to ensure that
     there are no workers running in KVM code when all references to
     KVM-the-module are gone, i.e. to prevent a very unlikely
     use-after-free if kvm.ko is unloaded

   - Grab a reference to the VM's mm_struct in the async #PF worker
     itself instead of gifting the worker a reference, so that there's
     no need to remember to *conditionally* clean up after the worker

  Selftests:

   - Reduce boilerplate especially when utilize selftest TAP
     infrastructure

   - Add basic smoke tests for SEV and SEV-ES, along with a pile of
     library support for handling private/encrypted/protected memory

   - Fix benign bugs where tests neglect to close() guest_memfd files"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits)
  selftests: kvm: remove meaningless assignments in Makefiles
  KVM: riscv: selftests: Add Zacas extension to get-reg-list test
  RISC-V: KVM: Allow Zacas extension for Guest/VM
  KVM: riscv: selftests: Add Ztso extension to get-reg-list test
  RISC-V: KVM: Allow Ztso extension for Guest/VM
  RISC-V: KVM: Forward SEED CSR access to user space
  KVM: riscv: selftests: Add sstc timer test
  KVM: riscv: selftests: Change vcpu_has_ext to a common function
  KVM: riscv: selftests: Add guest helper to get vcpu id
  KVM: riscv: selftests: Add exception handling support
  LoongArch: KVM: Remove unnecessary CSR register saving during enter guest
  LoongArch: KVM: Do not restart SW timer when it is expired
  LoongArch: KVM: Start SW timer only when vcpu is blocking
  LoongArch: KVM: Set reserved bits as zero in CPUCFG
  KVM: selftests: Explicitly close guest_memfd files in some gmem tests
  KVM: x86/xen: fix recursive deadlock in timer injection
  KVM: pfncache: simplify locking and make more self-contained
  KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
  KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled
  KVM: x86/xen: improve accuracy of Xen timers
  ...
2024-03-15 13:03:13 -07:00
Paolo Bonzini
e9a2bba476 KVM Xen and pfncache changes for 6.9:
- Rip out the half-baked support for using gfn_to_pfn caches to manage pages
    that are "mapped" into guests via physical addresses.
 
  - Add support for using gfn_to_pfn caches with only a host virtual address,
    i.e. to bypass the "gfn" stage of the cache.  The primary use case is
    overlay pages, where the guest may change the gfn used to reference the
    overlay page, but the backing hva+pfn remains the same.
 
  - Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
    of a gpa, so that userspace doesn't need to reconfigure and invalidate the
    cache/mapping if the guest changes the gpa (but userspace keeps the resolved
    hva the same).
 
  - When possible, use a single host TSC value when computing the deadline for
    Xen timers in order to improve the accuracy of the timer emulation.
 
  - Inject pending upcall events when the vCPU software-enables its APIC to fix
    a bug where an upcall can be lost (and to follow Xen's behavior).
 
  - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
    events fails, e.g. if the guest has aliased xAPIC IDs.
 
  - Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
    refresh), and drop a now-redundant acquisition of xen_lock (that was
    protecting the shared_info cache) to fix a deadlock due to recursively
    acquiring xen_lock.
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Merge tag 'kvm-x86-xen-6.9' of https://github.com/kvm-x86/linux into HEAD

KVM Xen and pfncache changes for 6.9:

 - Rip out the half-baked support for using gfn_to_pfn caches to manage pages
   that are "mapped" into guests via physical addresses.

 - Add support for using gfn_to_pfn caches with only a host virtual address,
   i.e. to bypass the "gfn" stage of the cache.  The primary use case is
   overlay pages, where the guest may change the gfn used to reference the
   overlay page, but the backing hva+pfn remains the same.

 - Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
   of a gpa, so that userspace doesn't need to reconfigure and invalidate the
   cache/mapping if the guest changes the gpa (but userspace keeps the resolved
   hva the same).

 - When possible, use a single host TSC value when computing the deadline for
   Xen timers in order to improve the accuracy of the timer emulation.

 - Inject pending upcall events when the vCPU software-enables its APIC to fix
   a bug where an upcall can be lost (and to follow Xen's behavior).

 - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
   events fails, e.g. if the guest has aliased xAPIC IDs.

 - Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
   refresh), and drop a now-redundant acquisition of xen_lock (that was
   protecting the shared_info cache) to fix a deadlock due to recursively
   acquiring xen_lock.
2024-03-11 10:42:55 -04:00
Paolo Bonzini
c9cd0beae9 KVM x86 misc changes for 6.9:
- Explicitly initialize a variety of on-stack variables in the emulator that
    triggered KMSAN false positives (though in fairness in KMSAN, it's comically
    difficult to see that the uninitialized memory is never truly consumed).
 
  - Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
    DR6 and DR7.
 
  - Rework the "force immediate exit" code so that vendor code ultimately
    decides how and when to force the exit.  This allows VMX to further optimize
    handling preemption timer exits, and allows SVM to avoid sending a duplicate
    IPI (SVM also has a need to force an exit).
 
  - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
    vCPU creation ultimately failed, and add WARN to guard against similar bugs.
 
  - Provide a dedicated arch hook for checking if a different vCPU was in-kernel
    (for directed yield), and simplify the logic for checking if the currently
    loaded vCPU is in-kernel.
 
  - Misc cleanups and fixes.
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Merge tag 'kvm-x86-misc-6.9' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.9:

 - Explicitly initialize a variety of on-stack variables in the emulator that
   triggered KMSAN false positives (though in fairness in KMSAN, it's comically
   difficult to see that the uninitialized memory is never truly consumed).

 - Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
   DR6 and DR7.

 - Rework the "force immediate exit" code so that vendor code ultimately
   decides how and when to force the exit.  This allows VMX to further optimize
   handling preemption timer exits, and allows SVM to avoid sending a duplicate
   IPI (SVM also has a need to force an exit).

 - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
   vCPU creation ultimately failed, and add WARN to guard against similar bugs.

 - Provide a dedicated arch hook for checking if a different vCPU was in-kernel
   (for directed yield), and simplify the logic for checking if the currently
   loaded vCPU is in-kernel.

 - Misc cleanups and fixes.
2024-03-11 10:24:56 -04:00