Re: [Qemu-devel] [PATCH 3/4] scsi-disk: introduce dma_readv and dma_writev

[Paolo Bonzini <pbonzini@redhat.com>]

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On 19/05/2016 17:11, Eric Blake wrote:
>> > @@ -339,14 +354,16 @@ static void scsi_do_read(SCSIDiskReq *r, int ret)
>> >      if (r->req.sg) {
>> >          dma_acct_start(s->qdev.conf.blk, &r->acct, r->req.sg, BLOCK_ACCT_READ);
>> >          r->req.resid -= r->req.sg->size;
>> > -        r->req.aiocb = dma_blk_read(s->qdev.conf.blk, r->req.sg, r->sector,
>> > -                                    scsi_dma_complete, r);
>> > +        r->req.aiocb = dma_blk_io(blk_get_aio_context(s->qdev.conf.blk),
>> > +                                  r->req.sg, r->sector,
>> > +                                  sdc->dma_readv, r, scsi_dma_complete, r,
>> > +                                  DMA_DIRECTION_FROM_DEVICE);
> 
> Is it worth considering byte-based rather than sector-based interfaces,
> as part of this series?

I think it's a separate change.  I'm okay with doing the switch to
byte-based interfaces first.  Another related change would be to add a
"mask" argument, so that I could generalize this:

    if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
        qemu_iovec_discard_back(&dbs->iov,
                                dbs->iov.size & ~BDRV_SECTOR_MASK);
    }

For this series the mask needs to be the logical block size.

Thanks,

Paolo


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