On Fri, May 03, 2013 at 10:45:22AM +0800, Liu Ping Fan wrote:
> From: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
>
> virtio-blk will unref RAM's memoryRegion when the io-req has been
> done. So we can avoid to call bdrv_drain_all() when RAM hot unplug.
>
> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
> ---
> hw/block/dataplane/virtio-blk.c | 51 +++++++++++++++++++++++++++++---------
> 1 files changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 3bb57d1..047e1df 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -35,6 +35,8 @@ enum {
>
> typedef struct {
> struct iocb iocb; /* Linux AIO control block */
> + MemoryRegion *mrs[VRING_MAX];
> + int mrs_cnt;
> QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
> unsigned int head; /* vring descriptor index */
> struct iovec *bounce_iov; /* used if guest buffers are unaligned */
> @@ -121,6 +123,10 @@ static void complete_request(struct iocb *iocb, ssize_t
> ret, void *opaque)
> * transferred plus the status bytes.
> */
> vring_push(&s->vring, req->head, len + sizeof(hdr));
> + while (--req->mrs_cnt >= 0) {
> + memory_region_unref(req->mrs[req->mrs_cnt]);
> + }
The vring has the property that every virtqueue element popped will be
pushed back.
Therefore it might be nicer to hide the MemoryRegion unref inside
vring_push(). The user wouldn't have to know about MemoryRegion -
that's especially nice since there are other devices besides virtio-blk
(like virtio-net) that would need to be modified if we use the current
approach.
Stefan
