Re: [RFC PATCH 00/29] KVM: VM planes

[Tom Lendacky <thomas.lendacky@amd.com>]

On 4/1/25 11:10, Paolo Bonzini wrote:
> I guess April 1st is not the best date to send out such a large series
> after months of radio silence, but here we are.

There were some miscellaneous fixes I had to apply to get the series to
compile and start working properly. I didn't break them out by patch #,
but here they are:

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 21dbc539cbe7..9d078eb001b1 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1316,32 +1316,35 @@ static void kvm_lapic_deliver_interrupt(struct kvm_vcpu *vcpu, struct kvm_lapic
 {
 	struct kvm_vcpu *plane0_vcpu = vcpu->plane0;
 	struct kvm_plane *running_plane;
+	int irr_pending_planes;
 	u16 req_exit_planes;
 
 	kvm_x86_call(deliver_interrupt)(apic, delivery_mode, trig_mode, vector);
 
 	/*
-	 * test_and_set_bit implies a memory barrier, so IRR is written before
+	 * atomic_fetch_or implies a memory barrier, so IRR is written before
 	 * reading irr_pending_planes below...
 	 */
-	if (!test_and_set_bit(vcpu->plane, &plane0_vcpu->arch.irr_pending_planes)) {
-		/*
-		 * ... and also running_plane and req_exit_planes are read after writing
-		 * irr_pending_planes.  Both barriers pair with kvm_arch_vcpu_ioctl_run().
-		 */
-		smp_mb__after_atomic();
+	irr_pending_planes = atomic_fetch_or(BIT(vcpu->plane), &plane0_vcpu->arch.irr_pending_planes);
+	if (irr_pending_planes & BIT(vcpu->plane))
+		return;
 
-		running_plane = READ_ONCE(plane0_vcpu->running_plane);
-		if (!running_plane)
-			return;
+	/*
+	 * ... and also running_plane and req_exit_planes are read after writing
+	 * irr_pending_planes.  Both barriers pair with kvm_arch_vcpu_ioctl_run().
+	 */
+	smp_mb__after_atomic();
 
-		req_exit_planes = READ_ONCE(plane0_vcpu->req_exit_planes);
-		if (!(req_exit_planes & BIT(vcpu->plane)))
-			return;
+	running_plane = READ_ONCE(plane0_vcpu->running_plane);
+	if (!running_plane)
+		return;
 
-		kvm_make_request(KVM_REQ_PLANE_INTERRUPT,
-				 kvm_get_plane_vcpu(running_plane, vcpu->vcpu_id));
-	}
+	req_exit_planes = READ_ONCE(plane0_vcpu->req_exit_planes);
+	if (!(req_exit_planes & BIT(vcpu->plane)))
+		return;
+
+	kvm_make_request(KVM_REQ_PLANE_INTERRUPT,
+			 kvm_get_plane_vcpu(running_plane, vcpu->vcpu_id));
 }
 
 /*
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 9d4492862c11..130d895f1d95 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -458,7 +458,7 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
 	INIT_LIST_HEAD(&sev->mirror_vms);
 	sev->need_init = false;
 
-	kvm_set_apicv_inhibit(kvm->planes[[0], APICV_INHIBIT_REASON_SEV);
+	kvm_set_apicv_inhibit(kvm->planes[0], APICV_INHIBIT_REASON_SEV);
 
 	return 0;
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 917bfe8db101..656b69eabc59 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3252,7 +3252,7 @@ static int interrupt_window_interception(struct kvm_vcpu *vcpu)
 	 * All vCPUs which run still run nested, will remain to have their
 	 * AVIC still inhibited due to per-cpu AVIC inhibition.
 	 */
-	kvm_clear_apicv_inhibit(vcpu->kvm, APICV_INHIBIT_REASON_IRQWIN);
+	kvm_clear_apicv_inhibit(vcpu->kvm->planes[vcpu->plane], APICV_INHIBIT_REASON_IRQWIN);
 
 	++vcpu->stat->irq_window_exits;
 	return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 65bc28e82140..704e8f80898f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11742,7 +11742,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		 * the other side will certainly see the cleared bit irr_pending_planes
 		 * and set it, and vice versa.
 		 */
-		clear_bit(plane_id, &plane0_vcpu->arch.irr_pending_planes);
+		atomic_and(~BIT(plane_id), &plane0_vcpu->arch.irr_pending_planes);
 		smp_mb__after_atomic();
 		if (kvm_lapic_find_highest_irr(vcpu))
 			atomic_or(BIT(plane_id), &plane0_vcpu->arch.irr_pending_planes);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3a04fdf0865d..efd45e05fddf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4224,7 +4224,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm_plane *plane, struct kvm_vcpu *pl
 	 * release semantics, which ensures the write is visible to kvm_get_vcpu().
 	 */
 	vcpu->plane = -1;
-	if (plane->plane)
+	if (!plane->plane)
 		vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus);
 	else
 		vcpu->vcpu_idx = plane0_vcpu->vcpu_idx;
@@ -4249,7 +4249,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm_plane *plane, struct kvm_vcpu *pl
 	if (r < 0)
 		goto kvm_put_xa_erase;
 
-	if (!plane0_vcpu)
+	if (!plane->plane)
 		atomic_inc(&kvm->online_vcpus);
 
 	/*

Thanks,
Tom

>