[PATCH v3 3/4] KVM: x86: Add lowest-priority support for vt-d posted-interrupts

[Feng Wu]

Use vector-hashing to deliver lowest-priority interrupts for
VT-d posted-interrupts. This patch extends kvm_intr_is_single_vcpu()
to support lowest-priority handling.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
v3:
- Remove unnecessary check in fast irq delivery patch
- print a error message only once for each guest when we find hardware
  disabled LAPIC during interrupt injection.

 arch/x86/include/asm/kvm_host.h |  4 +--
 arch/x86/kvm/irq_comm.c         |  8 +++---
 arch/x86/kvm/lapic.c            | 59 +++++++++++++++++++++++++++++++++++------
 arch/x86/kvm/lapic.h            |  4 +--
 arch/x86/kvm/vmx.c              |  2 +-
 5 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5054810..ce5a2ea 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1316,8 +1316,8 @@ int x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size);
 bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
 
-bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
-			     struct kvm_vcpu **dest_vcpu);
+bool kvm_intr_can_posting(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			  struct kvm_vcpu **dest_vcpu);
 
 void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
 		     struct kvm_lapic_irq *irq);
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 062e907..75cd02b 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -300,13 +300,13 @@ out:
 	return r;
 }
 
-bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
-			     struct kvm_vcpu **dest_vcpu)
+bool kvm_intr_can_posting(struct kvm *kvm, struct kvm_lapic_irq *irq,
+		struct kvm_vcpu **dest_vcpu)
 {
 	int i, r = 0;
 	struct kvm_vcpu *vcpu;
 
-	if (kvm_intr_is_single_vcpu_fast(kvm, irq, dest_vcpu))
+	if (kvm_intr_can_posting_fast(kvm, irq, dest_vcpu))
 		return true;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
@@ -325,7 +325,7 @@ bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
 
 	return r == 1;
 }
-EXPORT_SYMBOL_GPL(kvm_intr_is_single_vcpu);
+EXPORT_SYMBOL_GPL(kvm_intr_can_posting);
 
 #define IOAPIC_ROUTING_ENTRY(irq) \
 	{ .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,	\
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e1a449da..d22e87e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -800,7 +800,22 @@ out:
 	return ret;
 }
 
-bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+/*
+ * This routine tries to handler interrupts in posted mode, here is how
+ * it deals with different cases:
+ * - For single-destination interrupts, handle it in posted mode
+ * - Else if vector hashing is enabled and it is a lowest-priority
+ *   interrupt, handle it in posted mode and use the following mechanism
+ *   to find the destinaiton vCPU.
+ *	1. For lowest-priority interrupts, store all the possible
+ *	   destination vCPUs in an array.
+ *	2. Use "guest vector % max number of destination vCPUs" to find
+ *	   the right destination vCPU in the array for the lowest-priority
+ *	   interrupt.
+ * - Otherwise, use remapped mode to inject the interrupt.
+ */
+
+bool kvm_intr_can_posting_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
 			struct kvm_vcpu **dest_vcpu)
 {
 	struct kvm_apic_map *map;
@@ -841,16 +856,44 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
 		if (cid >= ARRAY_SIZE(map->logical_map))
 			goto out;
 
-		for_each_set_bit(i, &bitmap, 16) {
-			dst = map->logical_map[cid][i];
-			if (++r == 2)
+		if (kvm_vector_hashing_enabled() &&
+				kvm_lowest_prio_delivery(irq)) {
+			int idx = 0;
+			unsigned int dest_vcpus = 0;
+
+			dest_vcpus = hweight16(bitmap);
+			if (dest_vcpus == 0)
 				goto out;
-		}
 
-		if (dst && kvm_apic_present(dst->vcpu))
+			idx = kvm_vector_2_index(irq->vector, dest_vcpus,
+						 &bitmap, 16);
+
+			/*
+			 * We may find a hardware disabled LAPIC here, if that
+			 * is the case, print out a error message once for each
+			 * guest and return
+			 */
+			dst = map->logical_map[cid][idx-1];
+			if (!dst && (kvm->arch.disabled_lapic_found == 0)) {
+				kvm->arch.disabled_lapic_found = 1;
+				printk(KERN_ERR
+					"Disabled LAPIC found during irq injection\n");
+				goto out;
+			}
+
 			*dest_vcpu = dst->vcpu;
-		else
-			goto out;
+		} else {
+			for_each_set_bit(i, &bitmap, 16) {
+				dst = map->logical_map[cid][i];
+				if (++r == 2)
+					goto out;
+			}
+
+			if (dst && kvm_apic_present(dst->vcpu))
+				*dest_vcpu = dst->vcpu;
+			else
+				goto out;
+		}
 	}
 
 	ret = true;
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index d864601..6145939 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -173,8 +173,8 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
 
 void wait_lapic_expire(struct kvm_vcpu *vcpu);
 
-bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
-			struct kvm_vcpu **dest_vcpu);
+bool kvm_intr_can_posting_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			       struct kvm_vcpu **dest_vcpu);
 int kvm_vector_2_index(u32 vector, u32 dest_vcpus,
 		       const unsigned long *bitmap, u32 bitmap_size);
 #endif
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 13d14d4..b909ea1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10764,7 +10764,7 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
 		 */
 
 		kvm_set_msi_irq(e, &irq);
-		if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) {
+		if (!kvm_intr_can_posting(kvm, &irq, &vcpu)) {
 			/*
 			 * Make sure the IRTE is in remapped mode if
 			 * we don't handle it in posted mode.
-- 
2.1.0