[PATCH 1/4] KVM: Using kfifo for irq recording

[Sheng Yang <sheng@linux.intel.com>]

For MSI-X, we have to deal with multiply IRQ with same IRQ handler, so it's
necessary to record the IRQ that trigger the IRQ handler.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 include/linux/kvm_host.h |    4 ++++
 virt/kvm/kvm_main.c      |   30 +++++++++++++++++++++++++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5b671b6..541ccaf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -17,6 +17,7 @@
 #include <linux/preempt.h>
 #include <linux/marker.h>
 #include <linux/msi.h>
+#include <linux/kfifo.h>
 #include <asm/signal.h>
 
 #include <linux/kvm.h>
@@ -313,6 +314,9 @@ struct kvm_assigned_dev_kernel {
 	int host_irq;
 	bool host_irq_disabled;
 	int guest_irq;
+#define KVM_ASSIGNED_DEV_IRQ_FIFO_LEN	0x100
+	struct kfifo *irq_fifo;
+	spinlock_t irq_fifo_lock;
 #define KVM_ASSIGNED_DEV_GUEST_INTX	(1 << 0)
 #define KVM_ASSIGNED_DEV_GUEST_MSI	(1 << 1)
 #define KVM_ASSIGNED_DEV_HOST_INTX	(1 << 8)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e39c57a..3955e4d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -99,6 +99,8 @@ static struct kvm_assigned_dev_kernel *kvm_find_assigned_dev(struct list_head *h
 static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
 {
 	struct kvm_assigned_dev_kernel *assigned_dev;
+	int irq;
+	u32 gsi;
 
 	assigned_dev = container_of(work, struct kvm_assigned_dev_kernel,
 				    interrupt_work);
@@ -109,14 +111,22 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
 	 */
 	mutex_lock(&assigned_dev->kvm->lock);
 
-	kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
-		    assigned_dev->guest_irq, 1);
+handle_irq:
+	kfifo_get(assigned_dev->irq_fifo,
+		  (unsigned char *)&irq, sizeof(int));
+
+	gsi = assigned_dev->guest_irq;
+
+	kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id, gsi, 1);
 
 	if (assigned_dev->irq_requested_type & KVM_ASSIGNED_DEV_GUEST_MSI) {
 		enable_irq(assigned_dev->host_irq);
 		assigned_dev->host_irq_disabled = false;
 	}
 
+	if (kfifo_len(assigned_dev->irq_fifo) != 0)
+		goto handle_irq;
+
 	mutex_unlock(&assigned_dev->kvm->lock);
 	kvm_put_kvm(assigned_dev->kvm);
 }
@@ -128,6 +138,9 @@ static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id)
 
 	kvm_get_kvm(assigned_dev->kvm);
 
+	kfifo_put(assigned_dev->irq_fifo,
+		  (unsigned char *)&irq, sizeof(int));
+
 	schedule_work(&assigned_dev->interrupt_work);
 
 	disable_irq_nosync(irq);
@@ -201,6 +214,7 @@ static void kvm_free_assigned_device(struct kvm *kvm,
 	pci_dev_put(assigned_dev->dev);
 
 	list_del(&assigned_dev->list);
+	kfifo_free(assigned_dev->irq_fifo);
 	kfree(assigned_dev);
 }
 
@@ -449,15 +463,25 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 
 	list_add(&match->list, &kvm->arch.assigned_dev_head);
 
+	spin_lock_init(&match->irq_fifo_lock);
+	match->irq_fifo = kfifo_alloc(sizeof(unsigned char) *
+				      KVM_ASSIGNED_DEV_IRQ_FIFO_LEN,
+				      GFP_KERNEL | __GFP_ZERO,
+				      &match->irq_fifo_lock);
+	if (!match->irq_fifo)
+		goto out_list_del;
+
 	if (assigned_dev->flags & KVM_DEV_ASSIGN_ENABLE_IOMMU) {
 		r = kvm_iommu_map_guest(kvm, match);
 		if (r)
-			goto out_list_del;
+			goto out_fifo_del;
 	}
 
 out:
 	mutex_unlock(&kvm->lock);
 	return r;
+out_fifo_del:
+	kfifo_free(match->irq_fifo);
 out_list_del:
 	list_del(&match->list);
 	pci_release_regions(dev);
-- 
1.5.4.5