linux-kernel - [PATCH] KVM: nVMX: remove incorrect vpid check in nested invvpid emulation

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Message-Id: <1448443299-9375-1-git-send-email-haozhong.zhang@intel.com>
Date:	Wed, 25 Nov 2015 17:21:39 +0800
From:	Haozhong Zhang <haozhong.zhang@...el.com>
To:	kvm@...r.kernel.org
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Haozhong Zhang <haozhong.zhang@...el.com>
Subject: [PATCH] KVM: nVMX: remove incorrect vpid check in nested invvpid emulation

This patch removes the vpid check when emulating nested invvpid
instruction of type all-contexts invalidation. The existing code is
incorrect because:
 (1) According to Intel SDM Vol 3, Section "INVVPID - Invalidate
     Translations Based on VPID", invvpid instruction does not check
     vpid in the invvpid descriptor when its type is all-contexts
     invalidation.
 (2) According to the same document, invvpid of type all-contexts
     invalidation does not require there is an active VMCS, so/and
     get_vmcs12() in the existing code may result in a NULL-pointer
     dereference. In practice, it can crash both KVM itself and L1
     hypervisors that use invvpid (e.g. Xen).

Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
---
 arch/x86/kvm/vmx.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 87acc52..af823a3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7394,11 +7394,6 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 
 	switch (type) {
 	case VMX_VPID_EXTENT_ALL_CONTEXT:
-		if (get_vmcs12(vcpu)->virtual_processor_id == 0) {
-			nested_vmx_failValid(vcpu,
-				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
-			return 1;
-		}
 		__vmx_flush_tlb(vcpu, to_vmx(vcpu)->nested.vpid02);
 		nested_vmx_succeed(vcpu);
 		break;
-- 
2.4.8

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