linux-kernel - Re: [PATCH 08/11] KVM: selftests: Drop manual XCR0 configuration from AMX test

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Message-ID: <87iku8i69o.fsf@redhat.com>
Date: Fri, 04 Oct 2024 11:09:23 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/11] KVM: selftests: Drop manual XCR0 configuration
 from AMX test

Sean Christopherson <seanjc@...gle.com> writes:

> Now that CR4.OSXSAVE and XCR0 are setup by default, drop the manual
> enabling of OXSAVE and XTILE from the AMX test.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  tools/testing/selftests/kvm/x86_64/amx_test.c | 23 ++++---------------
>  1 file changed, 4 insertions(+), 19 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c
> index 903940c54d2d..f4ce5a185a7d 100644
> --- a/tools/testing/selftests/kvm/x86_64/amx_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
> @@ -86,6 +86,8 @@ static inline void __xsavec(struct xstate *xstate, uint64_t rfbm)
>  
>  static void check_xtile_info(void)
>  {
> +	GUEST_ASSERT((xgetbv(0) & XFEATURE_MASK_XTILE) == XFEATURE_MASK_XTILE);
> +
>  	GUEST_ASSERT(this_cpu_has_p(X86_PROPERTY_XSTATE_MAX_SIZE_XCR0));
>  	GUEST_ASSERT(this_cpu_property(X86_PROPERTY_XSTATE_MAX_SIZE_XCR0) <= XSAVE_SIZE);
>  
> @@ -122,29 +124,12 @@ static void set_tilecfg(struct tile_config *cfg)
>  	}
>  }
>  
> -static void init_regs(void)
> -{
> -	uint64_t cr4, xcr0;
> -
> -	GUEST_ASSERT(this_cpu_has(X86_FEATURE_XSAVE));
> -
> -	/* turn on CR4.OSXSAVE */
> -	cr4 = get_cr4();
> -	cr4 |= X86_CR4_OSXSAVE;
> -	set_cr4(cr4);
> -	GUEST_ASSERT(this_cpu_has(X86_FEATURE_OSXSAVE));
> -
> -	xcr0 = xgetbv(0);
> -	xcr0 |= XFEATURE_MASK_XTILE;
> -	xsetbv(0x0, xcr0);
> -	GUEST_ASSERT((xgetbv(0) & XFEATURE_MASK_XTILE) == XFEATURE_MASK_XTILE);
> -}
> -
>  static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg,
>  						    struct tile_data *tiledata,
>  						    struct xstate *xstate)
>  {
> -	init_regs();
> +	GUEST_ASSERT(this_cpu_has(X86_FEATURE_XSAVE) &&
> +		     this_cpu_has(X86_FEATURE_OSXSAVE));

Maybe 

        GUEST_ASSERT(get_cr4() & X86_CR4_OSXSAVE);

also (or instead), just like cr4_cpuid_sync_test?

>  	check_xtile_info();
>  	GUEST_SYNC(1);

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly