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Xin Li (Intel) fe85ee3919 x86/entry: Set FRED RSP0 on return to userspace instead of context switch
The FRED RSP0 MSR points to the top of the kernel stack for user level
event delivery. As this is the task stack it needs to be updated when a
task is scheduled in.

The update is done at context switch. That means it's also done when
switching to kernel threads, which is pointless as those never go out to
user space. For KVM threads this means there are two writes to FRED_RSP0 as
KVM has to switch to the guest value before VMENTER.

Defer the update to the exit to user space path and cache the per CPU
FRED_RSP0 value, so redundant writes can be avoided.

Provide fred_sync_rsp0() for KVM to keep the cache in sync with the actual
MSR value after returning from guest to host mode.

[ tglx: Massage change log ]

Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240822073906.2176342-4-xin@zytor.com
2024-08-25 19:23:00 +02:00
arch x86/entry: Set FRED RSP0 on return to userspace instead of context switch 2024-08-25 19:23:00 +02:00
block blk-throttle: remove more latency dead-code 2024-07-27 10:33:25 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation USB fixes for 6.11-rc3 2024-08-11 09:55:32 -07:00
drivers Three small fixes for interrupt core and drivers: 2024-08-11 10:07:52 -07:00
fs nfsd-6.11 fixes: 2024-08-10 10:44:21 -07:00
include i2c-for-6.11-rc3 2024-08-10 10:28:52 -07:00
init rust: SHADOW_CALL_STACK is incompatible with Rust 2024-08-01 16:15:03 +01:00
io_uring io_uring/net: don't pick multiple buffers for non-bundle send 2024-08-07 15:20:52 -06:00
ipc sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kernel Updates for time keeping: 2024-08-11 10:15:34 -07:00
lib minmax: don't use max() in situations that want a C constant expression 2024-07-28 20:23:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 9 hotfixes. 5 are cc:stable, 4 either pertain to post-6.10 material or 2024-08-08 07:32:20 -07:00
net nfsd-6.11 fixes: 2024-08-10 10:44:21 -07:00
rust rust: firmware: fix invalid rustdoc link 2024-07-31 13:24:29 +02:00
samples Driver core changes for 6.11-rc1 2024-07-25 10:42:22 -07:00
scripts syscalls: add back legacy __NR_nfsservctl macro 2024-08-06 08:57:02 +02:00
security apparmor-pr-2024-07-24 PR 2024-07-25 2024-07-27 13:28:39 -07:00
sound ASoC: Fixes for v6.11 2024-08-09 09:58:07 +02:00
tools Including fixes from bluetooth. 2024-08-08 13:51:44 -07:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: guest_memfd: abstract how prepared folios are recorded 2024-07-26 14:46:15 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap mailmap: update entry for David Heidelberg 2024-08-07 18:33:56 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS sound fixes for 6.11-rc3 2024-08-09 09:25:30 -07:00
Makefile Linux 6.11-rc3 2024-08-11 14:27:14 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.