Il 11/01/2013 13:39, Kevin Wolf ha scritto:
> Am 10.01.2013 17:48, schrieb Stefan Hajnoczi:
>> O_DIRECT on Linux has alignment requirements on I/O buffers and
>> misaligned requests result in -EINVAL. The Linux virtio_blk guest
>> driver usually submits aligned requests so I forgot to handle misaligned
>> requests.
>>
>> It turns out that virtio-win guest drivers submit misaligned requests.
>> Handle them using a bounce buffer that meets alignment requirements.
>>
>> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
>> ---
>> hw/dataplane/virtio-blk.c | 36 ++++++++++++++++++++++++++++++++++++
>> 1 file changed, 36 insertions(+)
>>
>> diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
>> index a6696b8..991ab5f 100644
>> --- a/hw/dataplane/virtio-blk.c
>> +++ b/hw/dataplane/virtio-blk.c
>> @@ -34,6 +34,8 @@ typedef struct {
>> struct iocb iocb; /* Linux AIO control block */
>> QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
>> unsigned int head; /* vring descriptor index */
>> + void *bounce_buffer; /* used if guest buffers are unaligned
>> */
>> + QEMUIOVector *read_qiov; /* for read completion /w bounce buffer
>> */
>> } VirtIOBlockRequest;
>>
>> struct VirtIOBlockDataPlane {
>> @@ -89,6 +91,15 @@ static void complete_request(struct iocb *iocb, ssize_t
>> ret, void *opaque)
>>
>> trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
>>
>> + if (req->read_qiov) {
>> + assert(req->bounce_buffer);
>> + qemu_iovec_to_buf(req->read_qiov, 0, req->bounce_buffer, len);
>
> Shouldn't it be qemu_iovec_from_buf()?
Yes.
> Makes me wonder if qtest cases might be doable...
Anthony, what's going on with libqos? :)
In the meanwhile...
>> + qemu_iovec_destroy(req->read_qiov);
>> + g_slice_free(QEMUIOVector, req->read_qiov);
>> + }
>> +
>> + qemu_vfree(req->bounce_buffer);
>> +
>> qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr));
>> qemu_iovec_destroy(req->inhdr);
>> g_slice_free(QEMUIOVector, req->inhdr);
>> @@ -136,6 +147,29 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool
>> read,
>> QEMUIOVector *inhdr)
>> {
>> struct iocb *iocb;
>> + QEMUIOVector qiov;
>> + struct iovec bounce_iov;
>> + void *bounce_buffer = NULL;
>> + QEMUIOVector *read_qiov = NULL;
>> +
>> + qemu_iovec_init_external(&qiov, iov, iov_cnt);
>> + if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) {
... changing this to "if (1)" would be enough for testing with Linux guests.
Paolo
>> + /* Redirect I/O to aligned bounce buffer */
>> + bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size);
>> + bounce_iov.iov_base = bounce_buffer;
>> + bounce_iov.iov_len = qiov.size;
>> + iov = &bounce_iov;
>> + iov_cnt = 1;
>> +
>> + if (read) {
>> + /* Need to copy back from bounce buffer on completion */
>> + read_qiov = g_slice_new(QEMUIOVector);
>> + qemu_iovec_init(read_qiov, iov_cnt);
>> + qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size);
>
> This would have to be the original iov and iov_cnt, but they are already
> overwritten here.
>
>> + } else {
>> + qemu_iovec_to_buf(&qiov, 0, bounce_buffer, qiov.size);
>> + }
>> + }
>>
>> iocb = ioq_rdwr(&s->ioqueue, read, iov, iov_cnt, offset);
>>
>> @@ -143,6 +177,8 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool
>> read,
>> VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
>> req->head = head;
>> req->inhdr = inhdr;
>> + req->bounce_buffer = bounce_buffer;
>> + req->read_qiov = read_qiov;
>> return 0;
>> }
>
> Kevin
>
>
