Re: [Qemu-devel] buffer alignment for block backends

[Gerd Hoffmann <kraxel@redhat.com>]

On 04/09/09 15:30, Stefano Stabellini wrote:
> The userspace\kernelspace distinction does not make much sense in
> minios, but yes it provides an interface to communicate with blkback in
> dom0. This interface is used by block-vbd in qemu instead of
> block-raw-posix when run in minios.

Sit back, look again.  Do you really need it being page-aligned?

The xen block protocol can handle unaligned requests just fine.  The 
granted page is splitted into 512 sectors (8 pieces in case of 4k pages 
on x86).  You can then request only some of the of the sectors being 
transfered.  If you have two sectors with a 1024 byte offset to the page 
border you'll just ask for sectors 2+3.

cheers,
   Gerd