Re: [Qemu-devel] [PATCH V3 4/6] ide: orphan all buffered requests on DMA cancel

[Fam Zheng <famz@redhat.com>]

On Fri, 11/06 09:42, Peter Lieven wrote:
> If the guests canceles a DMA request we can prematurely
> invoke all callbacks of buffered requests and flag all them
> as orphaned. Ideally this avoids the need for draining all
> requests. For CDROM devices this works in 100% of all cases.
> 
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  hw/ide/pci.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/hw/ide/pci.c b/hw/ide/pci.c
> index d31ff88..a9e164e 100644
> --- a/hw/ide/pci.c
> +++ b/hw/ide/pci.c
> @@ -240,6 +240,22 @@ void bmdma_cmd_writeb(BMDMAState *bm, uint32_t val)
>      /* Ignore writes to SSBM if it keeps the old value */
>      if ((val & BM_CMD_START) != (bm->cmd & BM_CMD_START)) {
>          if (!(val & BM_CMD_START)) {
> +            /* First invoke the callbacks of all buffered requests
> +             * and flag those requests as orphaned. Ideally there
> +             * are no unbuffered (Scatter Gather DMA Requests or
> +             * write requests) pending and we can avoid to drain. */
> +            IDEBufferedRequest *req;
> +            IDEState *s = idebus_active_if(bm->bus);
> +            QLIST_FOREACH(req, &s->buffered_requests, list) {
> +                if (!req->orphaned) {
> +#ifdef DEBUG_IDE
> +                    printf("%s: invoking cb %p of buffered request %p with"
> +                           " -ECANCELED\n", __func__, req->original_cb, req);
> +#endif
> +                    req->original_cb(req->original_opaque, -ECANCELED);
> +                }
> +                req->orphaned = true;
> +            }

Why not use bdrv_aio_cancel or bdrv_aio_cancel_async with the aio returned by
bdrv_aio_cancel?

Fam

>              /*
>               * We can't cancel Scatter Gather DMA in the middle of the
>               * operation or a partial (not full) DMA transfer would reach
> @@ -253,6 +269,9 @@ void bmdma_cmd_writeb(BMDMAState *bm, uint32_t val)
>               * aio operation with preadv/pwritev.
>               */
>              if (bm->bus->dma->aiocb) {
> +#ifdef DEBUG_IDE
> +                printf("%s: draining all remaining requests", __func__);
> +#endif
>                  blk_drain_all();
>                  assert(bm->bus->dma->aiocb == NULL);
>              }
> -- 
> 1.9.1
> 
>