[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>
ipxe · Jan 22, 2017 · e45451c · e45451c
1 parent dfbbc16
commit e45451c
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git 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
@@ -95,21 +95,21 @@ 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 */
 
    pa = virt_to_phys(queue);
    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;