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Peter Zijlstra 6204aea36b KVM: x86: Introduce EM_ASM_1
Replace fastops with C based stubs. There are a bunch of problems with
the current fastop infrastructure, most all related to their special
calling convention, which bypasses the normal C-ABI.

There are two immediate problems with this at present:

 - it relies on RET preserving EFLAGS; whereas C-ABI does not.

 - it circumvents compiler based control-flow-integrity checking
   because its all asm magic.

The first is a problem for some mitigations where the
x86_indirect_return_thunk needs to include non-trivial work that
clobbers EFLAGS (eg. the Skylake call depth tracking thing).

The second is a problem because it presents a 'naked' indirect call on
kCFI builds, making it a prime target for control flow hijacking.

Additionally, given that a large chunk of virtual machine performance
relies on absolutely avoiding vmexit these days, this emulation stuff
just isn't that critical for performance anymore.

As such, replace the fastop calls with normal C functions using the
'execute' member.

As noted by Paolo: this code was performance critical for pre-Westmere
(2010) and only when running big real mode code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lkml.kernel.org/r/20250714103439.773781574@infradead.org
History 2025-08-18 14:23:05 +02:00
arch KVM: x86: Introduce EM_ASM_1 2025-08-18 14:23:05 +02:00
block block: restore default wbt enablement 2025-08-13 05:33:48 -06:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
Documentation - Remove a transitional asm/cpuid.h header which was added only as 2025-08-17 06:53:15 -07:00
drivers - Remove a transitional asm/cpuid.h header which was added only as 2025-08-17 06:53:15 -07:00
fs xfs: Fixes for 6.17-rc2 2025-08-15 12:50:12 -07:00
include - Make sure sanity checks down in the mutex lock path happen on the correct 2025-08-17 05:57:47 -07:00
init Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
io_uring io_uring/io-wq: add check free worker before create new worker 2025-08-13 06:31:10 -06:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel - Make sure sanity checks down in the mutex lock path happen on the correct 2025-08-17 05:57:47 -07:00
lib Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/mremap: avoid expensive folio lookup on mremap folio pte batch 2025-08-11 23:00:59 -07:00
net Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
rust rust: kbuild: clean output before running rustdoc 2025-08-12 21:10:50 +02:00
samples Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
scripts Kbuild updates for v6.17 2025-08-06 07:32:52 +03:00
security + Features 2025-08-04 08:17:28 -07:00
sound ALSA: hda/tas2781: Normalize the volume kcontrol name 2025-08-14 11:17:12 +02:00
tools Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.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 Kbuild updates for v6.17 2025-08-06 07:32:52 +03:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
Makefile Linux 6.17-rc2 2025-08-17 15:22:10 -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.