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Date: Wed, 20 Jul 2011 18:18:43 +0200
From: Jan Kiszka <jan.kiszka@siemens.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: Avi Kivity <avi@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, "Michael S. Tsirkin" <mst@redhat.com>

On 2011-07-20 18:17, 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.

No, it isn't routed like that. The mask used via mmio is 0xfff.

Jan

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