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Date: Mon, 08 Aug 2011 08:02:08 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH v3 01/39] virtio-pci: get config on init
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Avi Kivity <avi@redhat.com>, kvm@vger.kernel.org, qemu-devel@nongnu.org

On 08/08/2011 07:56 AM, Michael S. Tsirkin wrote:
> On Mon, Aug 08, 2011 at 07:45:19AM -0500, Anthony Liguori wrote:
>> On 08/08/2011 05:36 AM, Michael S. Tsirkin wrote:
>>>> Thinking more closely, I don't think this right.
>>>>
>>>> Updating on map ensured that the config was refreshed after each
>>>> time the bar was mapped.  In the very least, the config needs to be
>>>> refreshed during reset because the guest may write to the guest
>>>> space which should get cleared after reset.
>>>>
>>>> Regards,
>>>>
>>>> Anthony Liguori
>>>
>>> Not sure I understand. Which register, for example,
>>> do you have in mind?
>>> Could you clarify please?
>>
>> Actually, you never need to call config_get() AFAICT.  It's called
>> in every read/write access.
>
> Every read, yes. But every write? Are you sure?

Yeah, not on write, but I think this is a bug.  get_config() should be 
called before doing the memcpy() in order to have a proper RMW.

Regards,

Anthony Liguori

>
>>   So I think the code you changed is
>> extraneous now.
>>
>> Regards,
>>
>> Anthony Liguori
>
>