[PATCH 19/19] Revert "KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu"

[Sean Christopherson <seanjc@google.com>]

Turns out that some warnings exist for good reasons.  Restore the warning
in avic_vcpu_load() that guards against calling avic_vcpu_load() on a
running vCPU now that KVM avoids doing so when switching between x2APIC
and xAPIC.  The entire point of the WARN is to highlight that KVM should
not be reloading an AVIC.

Opportunistically convert the WARN_ON() to WARN_ON_ONCE() to avoid
spamming the kernel if it does fire.

This reverts commit c0caeee65af3944b7b8abbf566e7cc1fae15c775.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/avic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index b2033a56010c..3c300113d40b 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1080,6 +1080,7 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		return;
 
 	entry = READ_ONCE(*(svm->avic_physical_id_cache));
+	WARN_ON_ONCE(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
 
 	entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
 	entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
-- 
2.37.2.672.g94769d06f0-goog