Re: [Qemu-devel] [PATCH 3/5] Implement fw_cfg DMA interface

[Kevin O'Connor]

On Thu, Aug 06, 2015 at 04:59:15PM +0200, Marc Marí wrote:
> On Thu, 6 Aug 2015 10:47:21 -0400
> "Kevin O'Connor" <address@hidden> wrote:
> > Also, it's very unusual to see 32bit writes to an unaligned IO address
> > - I think two pad bytes should be added so that the offset for the dma
> > address is at position 4 (instead of 2).
> 
> This is a PIO port (out), not a MMIO access (write). Maybe I'm wrong,
> but I don't think it matters to have the port number aligned with the
> write size.

There was a thread on misaligned IO accesses recently:

  http://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg05054.html

Perhaps Stefan knows what the implications of misaligned IO writes
are.

I suspect it's better to avoid them.

-Kevin