KVM: SVM: Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active

commit d02e488 upstream.

Commit 3bbf356 ("svm: Do not intercept CR8 when enable AVIC")
inhibited pre-VMRUN sync of TPR from LAPIC into VMCB::V_TPR in
sync_lapic_to_cr8() when AVIC is active.

AVIC does automatically sync between these two fields, however it does
so only on explicit guest writes to one of these fields, not on a bare
VMRUN.

This meant that when AVIC is enabled host changes to TPR in the LAPIC
state might not get automatically copied into the V_TPR field of VMCB.

This is especially true when it is the userspace setting LAPIC state via
KVM_SET_LAPIC ioctl() since userspace does not have access to the guest
VMCB.

Practice shows that it is the V_TPR that is actually used by the AVIC to
decide whether to issue pending interrupts to the CPU (not TPR in TASKPRI),
so any leftover value in V_TPR will cause serious interrupt delivery issues
in the guest when AVIC is enabled.

Fix this issue by doing pre-VMRUN TPR sync from LAPIC into VMCB::V_TPR
even when AVIC is enabled.

Fixes: 3bbf356 ("svm: Do not intercept CR8 when enable AVIC")
Cc: stable@vger.kernel.org
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/c231be64280b1461e854e1ce3595d70cde3a2e9d.1756139678.git.maciej.szmigiero@oracle.com
[sean: tag for stable@]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: maciejsszmigiero

arch/x86/kvm/svm/svm.c

@@ -3834,8 +3834,7 @@ static inline void sync_lapic_to_cr8(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 	u64 cr8;
 
-	if (nested_svm_virtualize_tpr(vcpu) ||
-	    kvm_vcpu_apicv_active(vcpu))
+	if (nested_svm_virtualize_tpr(vcpu))
 		return;
 
 	cr8 = kvm_get_cr8(vcpu);