linux-kernel - Re: [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation

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Message-ID: <5de81ced-c083-25e1-8954-6c232b9a7acd@redhat.com>
Date:   Thu, 9 Mar 2017 11:43:12 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     bdas@...hat.com, dmatlack@...gle.com
Subject: Re: [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation

Am 08.03.2017 um 19:03 schrieb Paolo Bonzini:
> handle_ept_violation is checking for "guest-linear-address invalid" +
> "paging-structure walk", which is a sign of a bug in KVM.  However,
> _all_ EPT violations without a valid guest linear address are paging
> structure walks, because those EPT violations happen when loading the
> guest PDPTEs.  So simplify the check to only look at bit 7 of the
> exit qualification.

Do we have any define for this magic bit 7?

#EPT_EXITQ_GLA_VALID 0x80

> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/vmx.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 89b74d9bc357..cb9034601c7b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6232,12 +6232,10 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  	unsigned long exit_qualification;
>  	gpa_t gpa;
>  	u32 error_code;
> -	int gla_validity;
>  
>  	exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
>  
> -	gla_validity = (exit_qualification >> 7) & 0x3;
> -	if (gla_validity == 0x2) {
> +	if ((exit_qualification & 0x80) == 0) {
>  		printk(KERN_ERR "EPT: Handling EPT violation failed!\n");
>  		printk(KERN_ERR "EPT: GPA: 0x%lx, GVA: 0x%lx\n",
>  			(long unsigned int)vmcs_read64(GUEST_PHYSICAL_ADDRESS),
> 


-- 
Thanks,

David