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Date: Wed, 20 Jul 2011 19:19:07 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] pci: Length-align config space accesses
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To: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>

On Thu, Jul 21, 2011 at 01:17:02AM +0900, Isaku Yamahata wrote:
> On Wed, Jul 20, 2011 at 04:27:08PM +0200, Jan Kiszka wrote:
> > On 2011-07-20 14:15, Jan Kiszka wrote:
> > > On 2011-07-20 14:00, Isaku Yamahata wrote:
> > >> Hi. This clean up looks good basically.
> > > 
> > > Oops, forgot to cc you. Sorry.
> > > 
> > >> But when conventional pci device is accessed via MMCONFIG area,
> > >> addr &= addr_mask doesn't work as expected.
> > >> The config area of [256, 4K) of conventional pci should have no effect.
> > > 
> > > Mmh, I see. Looks like we need to split accesses at this boundary and
> > > executed them separately.
> > 
> > Nope, no such issue: we already automatically split up accesses that
> > span the legacy/extended boundary. Just like so far, legacy config space
> > handlers have to filter out requests that address regions >= 256.
> 
> For example, when accessing to offset 257 of conventional pci device,
> the access is routed to offset 1 due to the masking.
> Such overwrapping isn't correct.

Can guest trigger this on some systems? I think it can't on a pc, right?

> -- 
> yamahata