Commit 782f6455 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: SVM: Skip AVIC and IRTE updates when loading blocking vCPU 



Don't bother updating the Physical APIC table or IRTE when loading a vCPU
that is blocking, i.e. won't be marked IsRun{ning}=1, as the pCPU is
queried if and only if IsRunning is '1'.  If the vCPU was migrated, the
new pCPU will be picked up when avic_vcpu_load() is called by
svm_vcpu_unblocking().

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20211208015236.1616697-15-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent af52f5aa

arch/x86/kvm/svm/avic.c

+18 −14
Original line number Diff line number Diff line
@@ -975,7 +975,6 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
{

	u64 entry;

	/* ID = 0xff (broadcast), ID > 0xff (reserved) */

	bool is_blocking = kvm_vcpu_is_blocking(vcpu);

	int h_physical_id = kvm_cpu_get_apicid(cpu);

	struct vcpu_svm *svm = to_svm(vcpu);
@@ -986,24 +985,25 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
	if (WARN_ON(h_physical_id > AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK))

		return;



	/*

	 * No need to update anything if the vCPU is blocking, i.e. if the vCPU

	 * is being scheduled in after being preempted.  The CPU entries in the

	 * Physical APIC table and IRTE are consumed iff IsRun{ning} is '1'.

	 * If the vCPU was migrated, its new CPU value will be stuffed when the

	 * vCPU unblocks.

	 */

	if (kvm_vcpu_is_blocking(vcpu))

		return;



	entry = READ_ONCE(*(svm->avic_physical_id_cache));

	WARN_ON(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);



	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;



	/*

	 * Don't mark the vCPU as running if its blocking, i.e. if the vCPU is

	 * preempted after svm_vcpu_blocking() but before KVM voluntarily

	 * schedules out the vCPU.

	 */

	if (!is_blocking)

	entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;



	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);

	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, !is_blocking);

	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, true);

}



void avic_vcpu_put(struct kvm_vcpu *vcpu)
@@ -1012,7 +1012,11 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu) 
	struct vcpu_svm *svm = to_svm(vcpu);



	entry = READ_ONCE(*(svm->avic_physical_id_cache));

	if (entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK)



	/* Nothing to do if IsRunning == '0' due to vCPU blocking. */

	if (!(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK))

		return;



	avic_update_iommu_vcpu_affinity(vcpu, -1, 0);



	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;