linux-kernel - [PATCH 1/2] KVM: VMX: Fix x2APIC MSR intercept handling on !APICV platforms

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Date:   Mon,  5 Oct 2020 12:55:31 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Alexander Graf <graf@...zon.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Peter Xu <peterx@...hat.com>
Subject: [PATCH 1/2] KVM: VMX: Fix x2APIC MSR intercept handling on !APICV platforms

From: Peter Xu <peterx@...hat.com>

Fix an inverted flag for intercepting x2APIC MSRs and intercept writes
by default, even when APICV is enabled.

Fixes: 3eb900173c71 ("KVM: x86: VMX: Prevent MSR passthrough when MSR access is denied")
Not-signed-off-by: Peter Xu <peterx@...hat.com>
[sean: added changelog]
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4551a7e80ebc..25ef0b22ac9e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3787,9 +3787,10 @@ static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode)
 	int msr;
 
 	for (msr = 0x800; msr <= 0x8ff; msr++) {
-		bool intercepted = !!(mode & MSR_BITMAP_MODE_X2APIC_APICV);
+		bool apicv = !!(mode & MSR_BITMAP_MODE_X2APIC_APICV);
 
-		vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_RW, intercepted);
+		vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_R, !apicv);
+		vmx_set_intercept_for_msr(vcpu, msr, MSR_TYPE_W, true);
 	}
 
 	if (mode & MSR_BITMAP_MODE_X2APIC) {
-- 
2.28.0