Re: [PATCH v3 06/13] KVM: selftests: x86: Add the XFD check to IA32_XFD in #NM handler

[Sean Christopherson]

On Tue, Feb 21, 2023, Mingwei Zhang wrote:
> Add an extra check to IA32_XFD to ensure the behavior is consistent with
> the AMX archtecture. In addition, repeat the checks across context switch
> to ensure the values of IA32_XFD and IA32_XFD_ERR are well preserved.
> 
> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/x86_64/amx_test.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c
> index ac49b14460b6..296c954dfd6d 100644
> --- a/tools/testing/selftests/kvm/x86_64/amx_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
> @@ -218,8 +218,10 @@ void guest_nm_handler(struct ex_regs *regs)
>  	GUEST_SYNC(7);
>  	GUEST_ASSERT((get_cr0() & X86_CR0_TS) == 0);
>  	GUEST_ASSERT(rdmsr(MSR_IA32_XFD_ERR) == XFEATURE_MASK_XTILEDATA);
> +	GUEST_ASSERT(rdmsr(MSR_IA32_XFD) & XFEATURE_MASK_XTILEDATA);

These should use ==, not &.  The test explicitly writes MSR_IA32_XFD, i.e. if
there are extra bits set then something is buggy.