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

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Date:   Wed,  8 Mar 2017 19:03:52 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     bdas@...hat.com, dmatlack@...gle.com
Subject: [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation

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.

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),
-- 
1.8.3.1