[PATCH RFC] virtio-pci: share config interrupt between virtio devices

Amos Kong
2014-09-01T05:41:54Z

One VM only has 128 msix interrupt, virtio-config interrupt
has less workload. This patch shares one normal interrupt
for configuration between virtio devices.

Signed-off-by: Amos Kong <akong@redhat.com>
---
drivers/virtio/virtio_pci.c | 41 ++++++++++++++++-------------------------
1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 3d1463c..b1263b3 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -52,6 +52,7 @@ struct virtio_pci_device
/* Name strings for interrupts. This size should be enough,
* and I'm too lazy to allocate each name separately. */
char (*msix_names)[256];
+ char config_msix_name[256];
/* Number of available vectors */
unsigned msix_vectors;
/* Vectors allocated, excluding per-vq vectors if any */
@@ -282,12 +283,6 @@ static void vp_free_vectors(struct virtio_device *vdev)
free_cpumask_var(vp_dev->msix_affinity_masks[i]);

if (vp_dev->msix_enabled) {
- /* Disable the vector used for configuration */
- iowrite16(VIRTIO_MSI_NO_VECTOR,
- vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
- /* Flush the write out to device */
- ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
-
pci_disable_msix(vp_dev->pci_dev);
vp_dev->msix_enabled = 0;
}
@@ -339,24 +334,18 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
goto error;
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,
+ /* Set shared IRQ for configuration */
+ snprintf(vp_dev->config_msix_name, 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],
+ err = request_irq(vp_dev->pci_dev->irq,
+ vp_config_changed,
+ IRQF_SHARED,
+ vp_dev->config_msix_name,
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;
+ if (!err)
+ vp_dev->intx_enabled = 1;
+ else
goto error;
- }

if (!per_vq_vectors) {
/* Shared vector for all VQs */
@@ -535,14 +524,16 @@ static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
goto error_request;
} else {
if (per_vq_vectors) {
- /* Best option: one for change interrupt, one per vq. */
- nvectors = 1;
+ /* Best option: one normal interrupt for change,
+ one msix per vq. */
+ nvectors = 0;
for (i = 0; i < nvqs; ++i)
if (callbacks[i])
++nvectors;
} else {
- /* Second best: one for change, shared for all vqs. */
- nvectors = 2;
+ /* Second best: one normal interrupt for
+ change, share one msix for all vqs. */
+ nvectors = 1;
}

err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors);
--
1.9.3