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Subject[PATCH 00/23] x86: Support Intel Advanced Matrix Extensions (part 4)
Date
This is the last part of the effort to support AMX. This series follows the
KVM part:
https://lore.kernel.org/lkml/20211017151447.829495362@linutronix.de/

With AMX the FPU register state buffer which is part of
task_struct::thread::fpu is not going to be extended unconditionally for
all tasks on an AMX enabled system as that would waste minimum 8K per task.

AMX provides a mechanism to trap on first use. That trap will be utilized
to allocate a larger register state buffer when the task (process) has
permissions to use it. The default buffer task_struct will only carry
states up to AVX512.

The cost of XFD switching only matters for an AMX-enabled system. With the
cleanup of the KVM FPU handling, host-side XFD/AMX is completely
independent of guest-side XFD/AMX.

The per-task feature and size information helps to support dynamic features
organically compared to the old versions.

Each task has a unique sigframe length with dynamic features. sigaltstack()
has a new size checker to support a per-task sigframe size.

This version also fixes the syscall implementation and the XFD state
switching on hot paths.

Here is a summary of patches:

- At first, add arch-specific sigaltstack size check

- Establish a set of new syscalls to control dynamic XSTATE components

- Update infrastructure to prepare dynamic features

- Support XFD state and switching, and add buffer reallocation helpers

- Finally, enable AMX with XFD #NM handling

This series is based on:

git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/fpu-3-kvm

and a revision of the version in the tglx tree -- some bug fixes, polish,
and addressing Dave Hansen's feedback (noted on each patch):

git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/fpu

This comes with a large selftest suite which is going to be posted
separately. A preview along with the full series is available here:

git://github.com/intel/amx-linux.git amx

Thanks,
Chang

Chang S. Bae (15):
x86/fpu/xstate: Provide xstate_calculate_size()
x86/arch_prctl: Add controls for dynamic XSTATE components
x86/fpu/signal: Prepare for variable sigframe length
x86/fpu: Reset permission and fpstate on exec()
x86/cpufeatures: Add eXtended Feature Disabling (XFD) feature bit
x86/msr-index: Add MSRs for XFD
x86/fpu: Add XFD state to fpstate
x86/fpu: Update XFD state where required
x86/fpu/xstate: Add XFD #NM handler
x86/fpu/xstate: Add fpstate_realloc()/free()
x86/fpu/xstate: Prepare XSAVE feature table for gaps in state
component numbers
x86/fpu/amx: Define AMX state components and have it used for
boot-time checks
x86/fpu: Calculate the default sizes independently
x86/fpu: Add XFD handling for dynamic states
x86/fpu/amx: Enable the AMX feature in 64-bit mode

Thomas Gleixner (8):
signal: Add an optional check for altstack size
x86/signal: Implement sigaltstack size validation
x86/fpu: Add members to struct fpu to cache permission information
x86/fpu: Add fpu_state_config::legacy_features
x86/fpu: Add basic helpers for dynamically enabled features
x86/signal: Use fpu::__state_user_size for sigalt stack validation
x86/fpu: Prepare fpu_clone() for dynamically enabled features
x86/fpu: Add sanity checks for XFD

.../admin-guide/kernel-parameters.txt | 9 +
arch/Kconfig | 3 +
arch/x86/Kconfig | 17 +
arch/x86/include/asm/cpufeatures.h | 2 +
arch/x86/include/asm/fpu/api.h | 11 +
arch/x86/include/asm/fpu/sched.h | 2 +-
arch/x86/include/asm/fpu/types.h | 88 +++
arch/x86/include/asm/fpu/xstate.h | 21 +-
arch/x86/include/asm/msr-index.h | 2 +
arch/x86/include/asm/proto.h | 2 +-
arch/x86/include/uapi/asm/prctl.h | 4 +
arch/x86/kernel/cpu/cpuid-deps.c | 2 +
arch/x86/kernel/fpu/context.h | 2 +
arch/x86/kernel/fpu/core.c | 93 ++-
arch/x86/kernel/fpu/init.c | 9 +-
arch/x86/kernel/fpu/internal.h | 3 -
arch/x86/kernel/fpu/signal.c | 70 +--
arch/x86/kernel/fpu/xstate.c | 566 ++++++++++++++++--
arch/x86/kernel/fpu/xstate.h | 61 +-
arch/x86/kernel/process.c | 21 +-
arch/x86/kernel/signal.c | 64 +-
arch/x86/kernel/traps.c | 38 ++
include/linux/signal.h | 6 +
kernel/signal.c | 35 +-
24 files changed, 1008 insertions(+), 123 deletions(-)


base-commit: 672f086122b67b299aa89c6b5f647c20ef84157f
--
2.17.1

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