Re: [Qemu-devel] [PATCH] virtio-scsi: fix "written length" field in the used ring

[Michael S. Tsirkin]

On Mon, Apr 27, 2015 at 04:18:43PM +0200, Paolo Bonzini wrote:
> 
> 
> On 27/04/2015 16:04, Michael S. Tsirkin wrote:
> >> > Because virtio-blk uses a response footer and virtio-scsi uses a
> >> > response header, fixing virtio-blk is much harder.  You need to add a
> >> > new argument to virtqueue_push.  I'd really prefer someone else to do 
> >> > it...
> >> > 
> >> > Paolo
> > OK but what's the desired API?
> > Do you know the host length or might any part of iov
> > be dirty?
> 
> For a 1-sector request and a 2048+1 bytes iov, I know that I've written
> bytes 0-511 and byte 2048.
> 
> So I have to dirty all 2049 bytes, but the written length should be 512.
>  Right now we pass 2049 to virtqueue_push and write 2049 to the written
> length, I'd need another argument to pass the 512.
> 
> Paolo

OK, I sent a patch with a new API, pls take a look.
Can you implement your patch on top?