[PATCH 6/9] virtio_pci: harden MSI-X interrupts

[Jason Wang]

We used to synchronize pending MSI-X irq handlers via
synchronize_irq(), this may not work for the untrusted device which
may keep sending interrupts after reset which may lead unexpected
results. Similarly, we should not enable MSI-X interrupt until the
device is ready. So this patch fixes those two issues by:

1) switching to use disable_irq() to prevent the virtio interrupt
   handlers to be called after the device is reset.
2) using IRQF_NO_AUTOEN and enable the MSI-X irq during .ready()

This can make sure the virtio interrupt handler won't be called before
virtio_device_ready() and after reset.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/virtio/virtio_pci_common.c | 27 +++++++++++++++++++++------
 drivers/virtio/virtio_pci_common.h |  6 ++++--
 drivers/virtio/virtio_pci_legacy.c |  5 +++--
 drivers/virtio/virtio_pci_modern.c |  6 ++++--
 4 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index b35bb2d57f62..0b9523e6dd39 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -24,8 +24,8 @@ MODULE_PARM_DESC(force_legacy,
 		 "Force legacy mode for transitional virtio 1 devices");
 #endif
 
-/* wait for pending irq handlers */
-void vp_synchronize_vectors(struct virtio_device *vdev)
+/* disable irq handlers */
+void vp_disable_vectors(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	int i;
@@ -34,7 +34,20 @@ void vp_synchronize_vectors(struct virtio_device *vdev)
 		synchronize_irq(vp_dev->pci_dev->irq);
 
 	for (i = 0; i < vp_dev->msix_vectors; ++i)
-		synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
+		disable_irq(pci_irq_vector(vp_dev->pci_dev, i));
+}
+
+/* enable irq handlers */
+void vp_enable_vectors(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	int i;
+
+	if (vp_dev->intx_enabled)
+		return;
+
+	for (i = 0; i < vp_dev->msix_vectors; ++i)
+		enable_irq(pci_irq_vector(vp_dev->pci_dev, i));
 }
 
 /* the notify function used when creating a virt queue */
@@ -141,7 +154,8 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
 	snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
 		 "%s-config", name);
 	err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
-			  vp_config_changed, 0, vp_dev->msix_names[v],
+			  vp_config_changed, IRQF_NO_AUTOEN,
+			  vp_dev->msix_names[v],
 			  vp_dev);
 	if (err)
 		goto error;
@@ -160,7 +174,8 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
 		snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
 			 "%s-virtqueues", name);
 		err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
-				  vp_vring_interrupt, 0, vp_dev->msix_names[v],
+				  vp_vring_interrupt, IRQF_NO_AUTOEN,
+				  vp_dev->msix_names[v],
 				  vp_dev);
 		if (err)
 			goto error;
@@ -337,7 +352,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
 			 "%s-%s",
 			 dev_name(&vp_dev->vdev.dev), names[i]);
 		err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
-				  vring_interrupt, 0,
+				  vring_interrupt, IRQF_NO_AUTOEN,
 				  vp_dev->msix_names[msix_vec],
 				  vqs[i]);
 		if (err)
diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index beec047a8f8d..a235ce9ff6a5 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -102,8 +102,10 @@ static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
 	return container_of(vdev, struct virtio_pci_device, vdev);
 }
 
-/* wait for pending irq handlers */
-void vp_synchronize_vectors(struct virtio_device *vdev);
+/* disable irq handlers */
+void vp_disable_vectors(struct virtio_device *vdev);
+/* enable irq handlers */
+void vp_enable_vectors(struct virtio_device *vdev);
 /* the notify function used when creating a virt queue */
 bool vp_notify(struct virtqueue *vq);
 /* the config->del_vqs() implementation */
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index d62e9835aeec..bdf6bc667ab5 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -97,8 +97,8 @@ static void vp_reset(struct virtio_device *vdev)
 	/* Flush out the status write, and flush in device writes,
 	 * including MSi-X interrupts, if any. */
 	ioread8(vp_dev->ioaddr + VIRTIO_PCI_STATUS);
-	/* Flush pending VQ/configuration callbacks. */
-	vp_synchronize_vectors(vdev);
+	/* Disable VQ/configuration callbacks. */
+	vp_disable_vectors(vdev);
 }
 
 static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
@@ -194,6 +194,7 @@ static void del_vq(struct virtio_pci_vq_info *info)
 }
 
 static const struct virtio_config_ops virtio_pci_config_ops = {
+	.ready		= vp_enable_vectors,
 	.get		= vp_get,
 	.set		= vp_set,
 	.get_status	= vp_get_status,
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 30654d3a0b41..acf0f6b6381d 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -172,8 +172,8 @@ static void vp_reset(struct virtio_device *vdev)
 	 */
 	while (vp_modern_get_status(mdev))
 		msleep(1);
-	/* Flush pending VQ/configuration callbacks. */
-	vp_synchronize_vectors(vdev);
+	/* Disable VQ/configuration callbacks. */
+	vp_disable_vectors(vdev);
 }
 
 static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
@@ -380,6 +380,7 @@ static bool vp_get_shm_region(struct virtio_device *vdev,
 }
 
 static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
+	.ready		= vp_enable_vectors,
 	.get		= NULL,
 	.set		= NULL,
 	.generation	= vp_generation,
@@ -397,6 +398,7 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
 };
 
 static const struct virtio_config_ops virtio_pci_config_ops = {
+	.ready		= vp_enable_vectors,
 	.get		= vp_get,
 	.set		= vp_set,
 	.generation	= vp_generation,
-- 
2.25.1