[virtio] Cap queue size to MAX_QUEUE_NUM

vpm_find_vqs incorrectly accepted the host provided queue size with no
regard to iPXE's internal limitations. Virtio 1.0 makes it possible for
the driver to override the queue size to reduce memory requirements and
iPXE is a great use case for this feature.

Also removing the extra vq->vring.num assignment which is already
handled in vring_init.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

2 files changed, 10 insertions, 4 deletions

diff --git a/src/drivers/bus/virtio-pci.c b/src/drivers/bus/virtio-pci.c
index 3311595fb..1fcf9bae0 100644
--- a/src/drivers/bus/virtio-pci.c
+++ b/src/drivers/bus/virtio-pci.c
@@ -358,12 +358,18 @@ int vpm_find_vqs(struct virtio_pci_modern_device *vdev,
             return -EINVAL;
         }
 
+        if (size > MAX_QUEUE_NUM) {
+            /* iPXE networking tends to be not perf critical so there's no
+             * need to accept large queue sizes.
+             */
+            size = MAX_QUEUE_NUM;
+        }
+
         vq = &vqs[i];
         vq->queue_index = i;
 
         /* get offset of notification word for this vq */
         off = vpm_ioread16(vdev, &vdev->common, COMMON_OFFSET(queue_notify_off));
-        vq->vring.num = size;
 
         vring_init(&vq->vring, size, (unsigned char *)vq->queue);
 
diff --git a/src/include/ipxe/virtio-ring.h b/src/include/ipxe/virtio-ring.h
index 6ba550b5a..d2ded3007 100644
--- a/src/include/ipxe/virtio-ring.h
+++ b/src/include/ipxe/virtio-ring.h
@@ -95,7 +95,7 @@ static inline void vring_init(struct vring *vr,
    unsigned int i;
    unsigned long pa;
 
-        vr->num = num;
+   vr->num = num;
 
    /* physical address of desc must be page aligned */
 
@@ -103,13 +103,13 @@ static inline void vring_init(struct vring *vr,
    pa = (pa + PAGE_MASK) & ~PAGE_MASK;
    vr->desc = phys_to_virt(pa);
 
-        vr->avail = (struct vring_avail *)&vr->desc[num];
+   vr->avail = (struct vring_avail *)&vr->desc[num];
 
    /* physical address of used must be page aligned */
 
    pa = virt_to_phys(&vr->avail->ring[num]);
    pa = (pa + PAGE_MASK) & ~PAGE_MASK;
-        vr->used = phys_to_virt(pa);
+   vr->used = phys_to_virt(pa);
 
    for (i = 0; i < num - 1; i++)
            vr->desc[i].next = i + 1;