• Cornelia Huck's avatar
    virtio: Honour 'may_reduce_num' in vring_create_virtqueue · cf94db21
    Cornelia Huck authored
    vring_create_virtqueue() allows the caller to specify via the
    may_reduce_num parameter whether the vring code is allowed to
    allocate a smaller ring than specified.
    
    However, the split ring allocation code tries to allocate a
    smaller ring on allocation failure regardless of what the
    caller specified. This may cause trouble for e.g. virtio-pci
    in legacy mode, which does not support ring resizing. (The
    packed ring code does not resize in any case.)
    
    Let's fix this by bailing out immediately in the split ring code
    if the requested size cannot be allocated and may_reduce_num has
    not been specified.
    
    While at it, fix a typo in the usage instructions.
    
    Fixes: 2a2d1382 ("virtio: Add improved queue allocation API")
    Cc: stable@vger.kernel.org # v4.6+
    Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
    Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
    Reviewed-by: default avatarHalil Pasic <pasic@linux.ibm.com>
    Reviewed-by: default avatarJens Freimann <jfreimann@redhat.com>
    cf94db21
virtio_ring.c 61 KB