On Wed, Dec 29, 2021, Yang Zhong wrote:
> From: Jing Liu <jing2.liu@xxxxxxxxx>
>
> CPUID.0xD.1.EBX enumerates the size of the XSAVE area (in compacted
> format) required by XSAVES. If CPUID.0xD.i.ECX[1] is set for a state
> component (i), this state component should be located on the next
> 64-bytes boundary following the preceding state component in the
> compacted layout.
>
> Fix xstate_required_size() to follow the alignment rule. AMX is the
> first state component with 64-bytes alignment to catch this bug.
>
> Signed-off-by: Jing Liu <jing2.liu@xxxxxxxxx>
> Signed-off-by: Yang Zhong <yang.zhong@xxxxxxxxx>
> ---
> arch/x86/kvm/cpuid.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 07e9215e911d..148003e26cbb 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -42,7 +42,8 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
> if (xstate_bv & 0x1) {
> u32 eax, ebx, ecx, edx, offset;
> cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
> - offset = compacted ? ret : ebx;
> + /* ECX[1]: 64B alignment in compacted form */
> + offset = compacted ? ((ecx & 0x2) ? ALIGN(ret, 64) : ret) : ebx;
That is impressively difficult to read.
if (compacted)
offset = (ecx & 0x2) ? ALIGN(ret, 64) : ret;
else
offset = ebx;
> ret = max(ret, offset + eax);
> }
>
