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Vishal Annapurve 9f98a4f4e7 x86/tdx: Fix arch_safe_halt() execution for TDX VMs 
Direct HLT instruction execution causes #VEs for TDX VMs which is routed
to hypervisor via TDCALL. If HLT is executed in STI-shadow, resulting #VE
handler will enable interrupts before TDCALL is routed to hypervisor
leading to missed wakeup events, as current TDX spec doesn't expose
interruptibility state information to allow #VE handler to selectively
enable interrupts.

Commit bfe6ed0c67 ("x86/tdx: Add HLT support for TDX guests")
prevented the idle routines from executing HLT instruction in STI-shadow.
But it missed the paravirt routine which can be reached via this path
as an example:

	kvm_wait()       =>
        safe_halt()      =>
        raw_safe_halt()  =>
        arch_safe_halt() =>
        irq.safe_halt()  =>
        pv_native_safe_halt()

To reliably handle arch_safe_halt() for TDX VMs, introduce explicit
dependency on CONFIG_PARAVIRT and override paravirt halt()/safe_halt()
routines with TDX-safe versions that execute direct TDCALL and needed
interrupt flag updates. Executing direct TDCALL brings in additional
benefit of avoiding HLT related #VEs altogether.

As tested by Ryan Afranji:

  "Tested with the specjbb2015 benchmark. It has heavy lock contention which leads
   to many halt calls. TDX VMs suffered a poor score before this patchset.

   Verified the major performance improvement with this patchset applied."

Fixes: bfe6ed0c67 ("x86/tdx: Add HLT support for TDX guests")
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Ryan Afranji <afranji@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250228014416.3925664-3-vannapurve@google.com
History 2025-03-26 08:51:20 +01:00
arch x86/tdx: Fix arch_safe_halt() execution for TDX VMs 2025-03-26 08:51:20 +01:00
block A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
Documentation - Add infrastructure support to EDAC in order to be able to register memory 2025-03-25 14:00:26 -07:00
drivers - Add infrastructure support to EDAC in order to be able to register memory 2025-03-25 14:00:26 -07:00
fs A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
include - Add infrastructure support to EDAC in order to be able to register memory 2025-03-25 14:00:26 -07:00
init [ Merge note: this pull request depends on you having merged 2025-03-24 22:06:11 -07:00
io_uring A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel Updates for the VDSO infrastructure: 2025-03-25 11:30:42 -07:00
lib Updates for the VDSO infrastructure: 2025-03-25 11:30:42 -07:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
net A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
rust Locking changes for v6.15: 2025-03-24 20:55:03 -07:00
samples hardening updates for v6.15-rc1 2025-03-24 15:18:08 -07:00
scripts [ Merge note: this pull request depends on you having merged 2025-03-24 22:06:11 -07:00
security hardening updates for v6.15-rc1 2025-03-24 15:18:08 -07:00
sound A treewide hrtimer timer cleanup 2025-03-25 10:54:15 -07:00
tools - Some preparatory work to convert the mitigations machinery to mitigating 2025-03-25 13:30:18 -07:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-05 04:06:45 +09:00
virt vfs-6.15-rc1.misc 2025-03-24 09:13:50 -07:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.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 rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap platform-drivers-x86 for v6.14-5 2025-03-14 10:57:28 -10:00
.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 MAINTAINERS: Move Pavel to kernel.org address 2025-02-07 09:12:33 -08:00
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 - Add infrastructure support to EDAC in order to be able to register memory 2025-03-25 14:00:26 -07:00
Makefile [ Merge note: this pull request depends on you having merged 2025-03-24 22:06:11 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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.