commit e45451c6994f6e93729ee3860e45fa965483356f
author Ladi Prosek <lprosek@redhat.com> Fri Dec 16 10:54:32 2016 +0100
committer Michael Brown <mcb30@ipxe.org> Sun Jan 22 13:18:28 2017 +0000
tree 42a29a9d741bedf9e99aec7e84723c6dc12dcb55
parent dfbbc16ae392e8f4ab62e15a99cdfb32a06af557

[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>

src/drivers/bus/virtio-pci.c

diff --git a/src/drivers/bus/virtio-pci.c b/src/drivers/bus/virtio-pci.c
index 3311595..1fcf9ba 100644
--- a/src/drivers/bus/virtio-pci.c
+++ b/src/drivers/bus/virtio-pci.c
@@ -358,12 +358,18 @@
             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);
 

src/include/ipxe/virtio-ring.h

diff --git a/src/include/ipxe/virtio-ring.h b/src/include/ipxe/virtio-ring.h
index 6ba550b..d2ded30 100644
--- a/src/include/ipxe/virtio-ring.h
+++ b/src/include/ipxe/virtio-ring.h
@@ -95,7 +95,7 @@
    unsigned int i;
    unsigned long pa;
 
-        vr->num = num;
+   vr->num = num;
 
    /* physical address of desc must be page aligned */
 
@@ -103,13 +103,13 @@
    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;