Michael S. Tsirkin
2009-Jul-23 15:48 UTC
[PATCH 2/2] virtio: retry on vector assignment failure
virtio currently fails to find any vqs if the device supports msi-x but fails
to assign it to a queue. Turns out, this actually happens for old host kernels
which can't allocate a gsi for the vector. As a result guest does not use
virtio net. Fix this by retrying with less vectors and finally disabling msi
on such failures and falling back on regular interrupts.
Reported-by: Amit Shah <amit.shah at redhat.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
A slightly bigger patch was tested by Amit Shah and reported working,
this one has been made as small as possible for -rc inclusion.
Let's pospone bigger refactorings for 2.6.32.
drivers/virtio/virtio_pci.c | 130 +++++++++++++++++++++++-------------------
1 files changed, 71 insertions(+), 59 deletions(-)
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 4bff231..25c7995 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -278,27 +278,24 @@ static void vp_free_vectors(struct virtio_device *vdev)
vp_dev->msix_entries = NULL;
}
-static int vp_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
- int *options, int noptions)
-{
- int i;
- for (i = 0; i < noptions; ++i)
- if (!pci_enable_msix(dev, entries, options[i]))
- return options[i];
- return -EBUSY;
-}
-
-static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)
+static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs,
+ int nvectors)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
const char *name = dev_name(&vp_dev->vdev.dev);
unsigned i, v;
int err = -ENOMEM;
- /* We want at most one vector per queue and one for config changes.
- * Fallback to separate vectors for config and a shared for queues.
- * Finally fall back to regular interrupts. */
- int options[] = { max_vqs + 1, 2 };
- int nvectors = max(options[0], options[1]);
+
+ if (!nvectors) {
+ /* Can't allocate MSI-X vectors, use regular interrupt */
+ vp_dev->msix_vectors = 0;
+ err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
+ IRQF_SHARED, name, vp_dev);
+ if (err)
+ return err;
+ vp_dev->intx_enabled = 1;
+ return 0;
+ }
vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
GFP_KERNEL);
@@ -312,38 +309,31 @@ static int vp_request_vectors(struct virtio_device *vdev,
unsigned max_vqs)
for (i = 0; i < nvectors; ++i)
vp_dev->msix_entries[i].entry = i;
- err = vp_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries,
- options, ARRAY_SIZE(options));
- if (err < 0) {
- /* Can't allocate enough MSI-X vectors, use regular interrupt */
- vp_dev->msix_vectors = 0;
- err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
- IRQF_SHARED, name, vp_dev);
- if (err)
- goto error;
- vp_dev->intx_enabled = 1;
- } else {
- vp_dev->msix_vectors = err;
- vp_dev->msix_enabled = 1;
-
- /* Set the vector used for configuration */
- v = vp_dev->msix_used_vectors;
- snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
- "%s-config", name);
- err = request_irq(vp_dev->msix_entries[v].vector,
- vp_config_changed, 0, vp_dev->msix_names[v],
- vp_dev);
- if (err)
- goto error;
- ++vp_dev->msix_used_vectors;
+ err = pci_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, nvectors);
+ if (err > 0)
+ err = -ENOSPC;
+ if (err)
+ goto error;
+ vp_dev->msix_vectors = nvectors;
+ vp_dev->msix_enabled = 1;
+
+ /* Set the vector used for configuration */
+ v = vp_dev->msix_used_vectors;
+ snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
+ "%s-config", name);
+ err = request_irq(vp_dev->msix_entries[v].vector,
+ vp_config_changed, 0, vp_dev->msix_names[v],
+ vp_dev);
+ if (err)
+ goto error;
+ ++vp_dev->msix_used_vectors;
- iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
- /* Verify we had enough resources to assign the vector */
- v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
- if (v == VIRTIO_MSI_NO_VECTOR) {
- err = -EBUSY;
- goto error;
- }
+ iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
+ /* Verify we had enough resources to assign the vector */
+ v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
+ if (v == VIRTIO_MSI_NO_VECTOR) {
+ err = -EBUSY;
+ goto error;
}
if (vp_dev->msix_vectors && vp_dev->msix_vectors != max_vqs + 1)
{
@@ -499,23 +489,17 @@ static void vp_del_vqs(struct virtio_device *vdev)
vp_free_vectors(vdev);
}
-/* the config->find_vqs() implementation */
-static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
- struct virtqueue *vqs[],
- vq_callback_t *callbacks[],
- const char *names[])
+static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+ struct virtqueue *vqs[],
+ vq_callback_t *callbacks[],
+ const char *names[],
+ int max_vqs, int nvectors)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
u16 vector, per_vq_vector;
- int vectors = 0;
int i, err, allocated_vectors;
- /* How many vectors would we like? */
- for (i = 0; i < nvqs; ++i)
- if (callbacks[i])
- ++vectors;
-
- err = vp_request_vectors(vdev, vectors);
+ err = vp_request_vectors(vdev, max_vqs, nvectors);
if (err)
goto error_request;
@@ -543,6 +527,34 @@ error_request:
return PTR_ERR(vqs[i]);
}
+/* the config->find_vqs() implementation */
+static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+ struct virtqueue *vqs[],
+ vq_callback_t *callbacks[],
+ const char *names[])
+{
+ /* We want at most one vector per queue and one for config changes.
+ * Fallback to separate vectors for config and a shared for queues.
+ * Finally fall back to regular interrupts. */
+ int options[] = { 1, 2, 0 };
+ int vectors = 0;
+ int i, uninitialized_var(err);
+
+ /* How many vectors would we like? */
+ for (i = 0; i < nvqs; ++i)
+ if (callbacks[i])
+ ++vectors;
+ options[0] = vectors + 1;
+
+ for (i = 0; i < ARRAY_SIZE(options); ++i) {
+ err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
+ vectors, options[i]);
+ if (!err)
+ break;
+ }
+ return err;
+}
+
static struct virtio_config_ops virtio_pci_config_ops = {
.get = vp_get,
.set = vp_set,
--
1.6.2.5
Possibly Parallel Threads
Wisdom of the Ancients
