linux-kernel - Re: [PATCH] KVM: nSVM: check for EFER.SVME=1 before entering guest

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Date:   Wed, 18 Mar 2020 15:53:19 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: nSVM: check for EFER.SVME=1 before entering guest

Paolo Bonzini <pbonzini@...hat.com> writes:

> EFER is set for L2 using svm_set_efer, which hardcodes EFER_SVME to 1 and hides
> an incorrect value for EFER.SVME in the L1 VMCB.  Perform the check manually
> to detect invalid guest state.
>
> Reported-by: Krish Sadhukhan <krish.sadhukhan@...cle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/svm.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 08568ae9f7a1..2125c6ae5951 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3558,6 +3558,9 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
>  
>  static bool nested_vmcb_checks(struct vmcb *vmcb)
>  {
> +	if ((vmcb->save.efer & EFER_SVME) == 0)
> +		return false;
> +
>  	if ((vmcb->control.intercept & (1ULL << INTERCEPT_VMRUN)) == 0)
>  		return false;

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

-- 
Vitaly