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Fix an FPU invalidation bug on exec(), and fix a performance

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regression due to a missing setting of X86_FEATURE_OSXSAVE.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2023-08-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
 "Fix an FPU invalidation bug on exec(), and fix a performance
  regression due to a missing setting of X86_FEATURE_OSXSAVE"

* tag 'x86-urgent-2023-08-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Set X86_FEATURE_OSXSAVE feature after enabling OSXSAVE in CR4
  x86/fpu: Invalidate FPU state correctly on exec()
This commit is contained in:
Linus Torvalds 2023-08-26 10:57:29 -07:00
commit 28f20a1929
3 changed files with 9 additions and 3 deletions
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3
arch/x86/kernel/fpu/context.h
View file

@ -19,8 +19,7 @@
* FPU state for a task MUST let the rest of the kernel know that the
* FPU registers are no longer valid for this task.
*
* Either one of these invalidation functions is enough. Invalidate
* a resource you control: CPU if using the CPU for something else
* Invalidate a resource you control: CPU if using the CPU for something else
* (with preemption disabled), FPU for the current task, or a task that
* is prevented from running by the current task.
*/

2
arch/x86/kernel/fpu/core.c
View file

@ -679,7 +679,7 @@ static void fpu_reset_fpregs(void)
struct fpu *fpu = &current->thread.fpu;
fpregs_lock();
fpu__drop(fpu);
__fpu_invalidate_fpregs_state(fpu);
/*
* This does not change the actual hardware registers. It just
* resets the memory image and sets TIF_NEED_FPU_LOAD so a

7
arch/x86/kernel/fpu/xstate.c
View file

@ -882,6 +882,13 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
goto out_disable;
}
/*
* CPU capabilities initialization runs before FPU init. So
* X86_FEATURE_OSXSAVE is not set. Now that XSAVE is completely
* functional, set the feature bit so depending code works.
*/
setup_force_cpu_cap(X86_FEATURE_OSXSAVE);
print_xstate_offset_size();
pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
fpu_kernel_cfg.max_features,