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2bcb52a360
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>
97 lines
2.6 KiB
C
97 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __KVM_MM_H__
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#define __KVM_MM_H__ 1
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/*
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* Architectures can choose whether to use an rwlock or spinlock
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* for the mmu_lock. These macros, for use in common code
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* only, avoids using #ifdefs in places that must deal with
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* multiple architectures.
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*/
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#ifdef KVM_HAVE_MMU_RWLOCK
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#define KVM_MMU_LOCK_INIT(kvm) rwlock_init(&(kvm)->mmu_lock)
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#define KVM_MMU_LOCK(kvm) write_lock(&(kvm)->mmu_lock)
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#define KVM_MMU_UNLOCK(kvm) write_unlock(&(kvm)->mmu_lock)
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#else
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#define KVM_MMU_LOCK_INIT(kvm) spin_lock_init(&(kvm)->mmu_lock)
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#define KVM_MMU_LOCK(kvm) spin_lock(&(kvm)->mmu_lock)
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#define KVM_MMU_UNLOCK(kvm) spin_unlock(&(kvm)->mmu_lock)
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#endif /* KVM_HAVE_MMU_RWLOCK */
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struct kvm_follow_pfn {
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const struct kvm_memory_slot *slot;
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const gfn_t gfn;
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unsigned long hva;
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/* FOLL_* flags modifying lookup behavior, e.g. FOLL_WRITE. */
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unsigned int flags;
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/*
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* Pin the page (effectively FOLL_PIN, which is an mm/ internal flag).
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* The page *must* be pinned if KVM will write to the page via a kernel
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* mapping, e.g. via kmap(), mremap(), etc.
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*/
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bool pin;
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/*
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* If non-NULL, try to get a writable mapping even for a read fault.
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* Set to true if a writable mapping was obtained.
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*/
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bool *map_writable;
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/*
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* Optional output. Set to a valid "struct page" if the returned pfn
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* is for a refcounted or pinned struct page, NULL if the returned pfn
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* has no struct page or if the struct page is not being refcounted
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* (e.g. tail pages of non-compound higher order allocations from
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* IO/PFNMAP mappings).
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*/
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struct page **refcounted_page;
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};
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kvm_pfn_t hva_to_pfn(struct kvm_follow_pfn *kfp);
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#ifdef CONFIG_HAVE_KVM_PFNCACHE
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void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm,
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unsigned long start,
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unsigned long end);
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#else
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static inline void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm,
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unsigned long start,
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unsigned long end)
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{
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}
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#endif /* HAVE_KVM_PFNCACHE */
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#ifdef CONFIG_KVM_PRIVATE_MEM
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void kvm_gmem_init(struct module *module);
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int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args);
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int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
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unsigned int fd, loff_t offset);
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void kvm_gmem_unbind(struct kvm_memory_slot *slot);
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#else
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static inline void kvm_gmem_init(struct module *module)
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{
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}
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static inline int kvm_gmem_bind(struct kvm *kvm,
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struct kvm_memory_slot *slot,
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unsigned int fd, loff_t offset)
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{
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WARN_ON_ONCE(1);
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return -EIO;
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}
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static inline void kvm_gmem_unbind(struct kvm_memory_slot *slot)
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{
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WARN_ON_ONCE(1);
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}
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#endif /* CONFIG_KVM_PRIVATE_MEM */
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#endif /* __KVM_MM_H__ */
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