linux-kernel - Re: [PATCH] KVM: VMX: Expose SSBD properly to guests.

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Date:   Wed, 23 May 2018 01:50:55 +0200
From:   Ben Hutchings <ben@...adent.org.uk>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: Re: [PATCH] KVM: VMX: Expose SSBD properly to guests.

On Mon, 2018-05-21 at 17:54 -0400, Konrad Rzeszutek Wilk wrote:
> The X86_FEATURE_SSBD is an synthetic CPU feature - that is
> it bit location has no relevance to the real CPUID 0x7.EBX[31]
> bit position. For that we need the new CPU feature name.
> 
> Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
> 
> CC: Paolo Bonzini <pbonzini@...hat.com>
> Cc: "Radim Krčmář" <rkrcmar@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  arch/x86/kvm/cpuid.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ced851169730..598461e24be3 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -407,8 +407,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  
>  	/* cpuid 7.0.edx*/
>  	const u32 kvm_cpuid_7_0_edx_x86_features =
> -		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
> -		F(ARCH_CAPABILITIES);
> +		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> +		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
>  
>  	/* all calls to cpuid_count() should be made on the same cpu */
>  	get_cpu();

For 4.9-stable, guest_cpuid_has_spec_ctrl() needs a similar fix.

Ben.

-- 
Ben Hutchings
It is easier to change the specification to fit the program
than vice versa.

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