linux-kernel - Re: [PATCH 1/3] KVM: x86: block guest protection keys unless the host has them enabled

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Date:   Thu, 24 Aug 2017 19:54:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     junkang.fjk@...baba-inc.com, yang.zhang.wz@...il.com
Subject: Re: [PATCH 1/3] KVM: x86: block guest protection keys unless the host
 has them enabled

On 24.08.2017 12:12, Paolo Bonzini wrote:
> If the host has protection keys disabled, we cannot read and write the
> guest PKRU---RDPKRU and WRPKRU fail with #GP(0) if CR4.PKE=0.  Block
> the PKU cpuid bit in that case.
> 
> This ensures that guest_CR4.PKE=1 implies host_CR4.PKE=1.
> 
> Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/cpuid.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 59ca2eea522c..19adbb418443 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -469,7 +469,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  			entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
>  			cpuid_mask(&entry->ecx, CPUID_7_ECX);
>  			/* PKU is not yet implemented for shadow paging. */
> -			if (!tdp_enabled)
> +			if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
>  				entry->ecx &= ~F(PKU);
>  			entry->edx &= kvm_cpuid_7_0_edx_x86_features;
>  			entry->edx &= get_scattered_cpuid_leaf(7, 0, CPUID_EDX);
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 

Thanks,

David