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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Tue, 20 Sep 2022 23:31:30 +0000
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Message-ID: <20220920233134.940511-25-seanjc@google.com>
Subject: [PATCH v3 24/28] KVM: SVM: Update svm->ldr_reg cache even if LDR is "bad"
From:   Sean Christopherson <seanjc@google.com>
To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alejandro Jimenez <alejandro.j.jimenez@oracle.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        Li RongQing <lirongqing@baidu.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Update SVM's cache of the LDR even if the new value is "bad".  Leaving
stale information in the cache can result in KVM missing updates and/or
invalidating the wrong entry, e.g. if avic_invalidate_logical_id_entry()
is triggered after a different vCPU has "claimed" the old LDR.

Fixes: 18f40c53e10f ("svm: Add VMEXIT handlers for AVIC")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/avic.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 2b640c73f447..4b6fc9d64f4d 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -539,23 +539,24 @@ static u32 *avic_get_logical_id_entry(struct kvm_vcpu *vcpu, u32 ldr, bool flat)
 	return &logical_apic_id_table[index];
 }
 
-static int avic_ldr_write(struct kvm_vcpu *vcpu, u8 g_physical_id, u32 ldr)
+static void avic_ldr_write(struct kvm_vcpu *vcpu, u8 g_physical_id, u32 ldr)
 {
 	bool flat;
 	u32 *entry, new_entry;
 
+	if (!ldr)
+		return;
+
 	flat = kvm_lapic_get_reg(vcpu->arch.apic, APIC_DFR) == APIC_DFR_FLAT;
 	entry = avic_get_logical_id_entry(vcpu, ldr, flat);
 	if (!entry)
-		return -EINVAL;
+		return;
 
 	new_entry = READ_ONCE(*entry);
 	new_entry &= ~AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK;
 	new_entry |= (g_physical_id & AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK);
 	new_entry |= AVIC_LOGICAL_ID_ENTRY_VALID_MASK;
 	WRITE_ONCE(*entry, new_entry);
-
-	return 0;
 }
 
 static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
@@ -575,7 +576,6 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
 
 static void avic_handle_ldr_update(struct kvm_vcpu *vcpu)
 {
-	int ret = 0;
 	struct vcpu_svm *svm = to_svm(vcpu);
 	u32 ldr = kvm_lapic_get_reg(vcpu->arch.apic, APIC_LDR);
 	u32 id = kvm_xapic_id(vcpu->arch.apic);
@@ -589,11 +589,8 @@ static void avic_handle_ldr_update(struct kvm_vcpu *vcpu)
 
 	avic_invalidate_logical_id_entry(vcpu);
 
-	if (ldr)
-		ret = avic_ldr_write(vcpu, id, ldr);
-
-	if (!ret)
-		svm->ldr_reg = ldr;
+	svm->ldr_reg = ldr;
+	avic_ldr_write(vcpu, id, ldr);
 }
 
 static void avic_handle_dfr_update(struct kvm_vcpu *vcpu)
-- 
2.37.3.968.ga6b4b080e4-goog