Re: [Qemu-block] [RFC] ide: fix bmdma underflow code

[Stefan Hajnoczi]

On Mon, Jun 29, 2015 at 04:16:06PM -0400, John Snow wrote:
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 8c271cc..6bcf07c 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -716,8 +716,8 @@ static void ide_dma_cb(void *opaque, int ret)
>  
>      sector_num = ide_get_sector(s);
>      if (n > 0) {
> -        assert(s->io_buffer_size == s->sg.size);
> -        dma_buf_commit(s, s->io_buffer_size);
> +        assert(s->nsector * 512 == s->sg.size);

The short PRDT case:

nsector = 2 sectors
PRD length = 1 sector

After prepare_buf() io_buffer_size = 1 sector and sg.size = 1 sector.

When ide_dma_cb() is called again:
nsector = 2 sectors
sg.size = 1 sector

So this assertion fails?

The assertion can be dropped.


Anyway, I think this change is good.  Previously, IDE DMA transferred
the full PRDT and then completed the request.  Now it only transfers the
capped PRDT.

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