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

From: David Hildenbrand
Date: Thu Mar 09 2017 - 05:50:46 EST


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@xxxxxxxxxx>
> ---
> 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