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SubjectRe: [PATCH v8 07/26] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate
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On Thu, 2023-12-21 at 09:02 -0500, Yang Weijiang wrote:
> Kernel dynamic xfeatures now are __ONLY__ enabled for guest fpstate, i.e.,
> never for normal kernel fpstate. The bits are added when guest FPU config
> is initialized. Guest fpstate is allocated with fpstate->is_guest set to
> %true.
>
> For normal fpstate, the bits should have been removed when initializes
> kernel FPU config settings, WARN_ONCE() if kernel detects normal fpstate
> xfeatures contains kernel dynamic xfeatures before executes xsaves.
>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
> arch/x86/kernel/fpu/xstate.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
> index 3518fb26d06b..83ebf1e1cbb4 100644
> --- a/arch/x86/kernel/fpu/xstate.h
> +++ b/arch/x86/kernel/fpu/xstate.h
> @@ -185,6 +185,9 @@ static inline void os_xsave(struct fpstate *fpstate)
> WARN_ON_FPU(!alternatives_patched);
> xfd_validate_state(fpstate, mask, false);
>
> + WARN_ON_FPU(!fpstate->is_guest &&
> + (mask & XFEATURE_MASK_KERNEL_DYNAMIC));
> +
> XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);
>
> /* We should never fault when copying to a kernel buffer: */

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky


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