[virtio] Remove queue size limit in legacy virtio

Virtio 0.9 implementation was limited to the maximum virtqueue size of
MAX_QUEUE_NUM and the virtio-net driver would fail to initialize on hosts
exceeding this limit.

This commit lifts the restriction by allocating the queue memory based on
the actual queue size instead of using a fixed maximum. Note that virtio
1.0 still uses the MAX_QUEUE_NUM constant to cap the size (unfortunately
this functionality is not available in virtio 0.9).

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/include/ipxe/virtio-pci.h

@@ -196,9 +196,11 @@ static inline void vp_del_vq(unsigned int ioaddr, int queue_index)
 
 struct vring_virtqueue;
 
+void vp_free_vq(struct vring_virtqueue *vq);
 int vp_find_vq(unsigned int ioaddr, int queue_index,
                struct vring_virtqueue *vq);
 
+
 /* Virtio 1.0 I/O routines abstract away the three possible HW access
  * mechanisms - memory, port I/O, and PCI cfg space access. Also built-in
  * are endianness conversions - to LE on write and from LE on read. */

src/include/ipxe/virtio-ring.h

@@ -71,14 +71,12 @@ struct vring {
          + PAGE_MASK) & ~PAGE_MASK) + \
          (sizeof(struct vring_used) + sizeof(struct vring_used_elem) * num))
 
-typedef unsigned char virtio_queue_t[PAGE_MASK + vring_size(MAX_QUEUE_NUM)];
-
 struct vring_virtqueue {
-   virtio_queue_t queue;
+   unsigned char *queue;
    struct vring vring;
    u16 free_head;
    u16 last_used_idx;
-   void *vdata[MAX_QUEUE_NUM];
+   void **vdata;
    /* PCI */
    int queue_index;
    struct virtio_pci_region notification;