linux-kernel - [GIT PULL] x86/cpu for 6.19-rc1

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Message-Id: <20251201231537.736899-1-dave.hansen@linux.intel.com>
Date: Mon,  1 Dec 2025 15:15:37 -0800
From: Dave Hansen <dave.hansen@...ux.intel.com>
To: torvalds@...ux-foundation.org
Cc: x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [GIT PULL] x86/cpu for 6.19-rc1

Hi Linus,

Please pull some x86/cpu changes for 6.19-rc1. The biggest thing of
note here is Linear Address Space Separation (LASS). It represents the
first time I can think of that the upper=>kernel/lower=>user address
space convention is actually recognized by the hardware on x86. It
ensures that userspace can not even get the hardware to _start_ page
walks for the kernel address space. This, of course, is a really nice
generic side channel defense.

This is really only a down payment on LASS support. There are still
some details to work out in its interaction with EFI calls and
vsyscall emulation. For now, LASS is disabled if either of those
features is compiled in (which is almost always the case).

There's also one straggler commit in here which converts an
under-utilized AMD CPU feature leaf into a generic Linux-defined leaf
so more feature can be packed in there.

--

The following changes since commit 3a8660878839faadb4f1a6dd72c3179c1df56787:

  Linux 6.18-rc1 (2025-10-12 13:42:36 -0700)

are available in the Git repository at:

  https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git tags/x86_cpu_for_6.19-rc1

for you to fetch changes up to d5cb9574391cc0a4683c22944d00d0ad76a224d3:

  x86/cpu: Enable LASS during CPU initialization (2025-11-18 10:38:27 -0800)

----------------------------------------------------------------
 * Enable Linear Address Space Separation (LASS)
 * Change X86_FEATURE leaf 17 from an AMD leaf to Linux-defined

----------------------------------------------------------------
Alexander Shishkin (1):
      x86/traps: Communicate a LASS violation in #GP message

Borislav Petkov (AMD) (1):
      x86/cpufeatures: Make X86_FEATURE leaf 17 Linux-specific

Peter Zijlstra (Intel) (1):
      x86/asm: Introduce inline memcpy and memset

Sohil Mehta (6):
      x86/cpufeatures: Enumerate the LASS feature bits
      x86/cpu: Add an LASS dependency on SMAP
      x86/alternatives: Disable LASS when patching kernel code
      x86/kexec: Disable LASS during relocate kernel
      selftests/x86: Update the negative vsyscall tests to expect a #GP
      x86/cpu: Enable LASS during CPU initialization

 arch/x86/Kconfig.cpufeatures                |  4 +++
 arch/x86/include/asm/cpufeature.h           |  2 +-
 arch/x86/include/asm/cpufeatures.h          |  6 +++-
 arch/x86/include/asm/smap.h                 | 41 +++++++++++++++++++++++++--
 arch/x86/include/asm/string.h               | 26 +++++++++++++++++
 arch/x86/include/uapi/asm/processor-flags.h |  2 ++
 arch/x86/kernel/alternative.c               | 18 ++++++++++--
 arch/x86/kernel/cpu/common.c                | 32 ++++++++++++++++-----
 arch/x86/kernel/cpu/cpuid-deps.c            |  1 +
 arch/x86/kernel/cpu/scattered.c             |  3 ++
 arch/x86/kernel/relocate_kernel_64.S        |  7 +++--
 arch/x86/kernel/traps.c                     | 44 +++++++++++++++++++++--------
 arch/x86/kvm/reverse_cpuid.h                |  1 -
 tools/arch/x86/include/asm/cpufeatures.h    |  5 +++-
 tools/testing/selftests/x86/test_vsyscall.c | 21 ++++++++------
 15 files changed, 176 insertions(+), 37 deletions(-)