linux-kernel - [PATCH] KVM/VMX: Check ept_pointer before flushing ept tlb

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Message-Id: <20181106133043.83570-1-Tianyu.Lan@microsoft.com>
Date:   Tue,  6 Nov 2018 21:30:43 +0800
From:   ltykernel@...il.com
To:     unlisted-recipients:; (no To-header on input)
Cc:     Lan Tianyu <Tianyu.Lan@...rosoft.com>, pbonzini@...hat.com,
        rkrcmar@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, michael.h.kelley@...rosoft.com,
        kys@...rosoft.com, vkuznets@...hat.com
Subject: [PATCH] KVM/VMX: Check ept_pointer before flushing ept tlb

From: Lan Tianyu <Tianyu.Lan@...rosoft.com>

This patch is to initialize ept_pointer to INVALID_PAGE and check it
before flushing ept tlb. If ept_pointer is invalidated, bypass the flush
request.

Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
---
 arch/x86/kvm/vmx.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4555077d69ce..edbc96cb990a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1580,14 +1580,22 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
 	/*
 	 * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
 	 * base of EPT PML4 table, strip off EPT configuration information.
+	 * If ept_pointer is invalid pointer, bypass the flush request.
 	 */
 	if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
-		kvm_for_each_vcpu(i, vcpu, kvm)
+		kvm_for_each_vcpu(i, vcpu, kvm) {
+			if (!VALID_PAGE(to_vmx(vcpu)->ept_pointer))
+				return 0;
+
 			ret |= hyperv_flush_guest_mapping(
-				to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & PAGE_MASK);
+				to_vmx(vcpu)->ept_pointer & PAGE_MASK);
+		}
 	} else {
+		if (!VALID_PAGE(to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer))
+			return 0;
+
 		ret = hyperv_flush_guest_mapping(
-				to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
+			to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
 	}
 
 	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
@@ -11568,6 +11576,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 	vmx->pi_desc.nv = POSTED_INTR_VECTOR;
 	vmx->pi_desc.sn = 1;
 
+	vmx->ept_pointer = INVALID_PAGE;
+
 	return &vmx->vcpu;
 
 free_vmcs:
-- 
2.14.4