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Date: Mon, 14 Sep 2009 17:54:36 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: pci: is reset incomplete?
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Carsten Otte <cotte@de.ibm.com>, Gerd Hoffmann <kraxel@redhat.com>, kvm@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Christian Borntraeger <borntraeger@de.ibm.com>, Paul Brook <paul@codesourcery.com>, Avi Kivity <avi@redhat.com>

Michael S. Tsirkin wrote:
> On Mon, Sep 14, 2009 at 12:15:29PM -0500, Anthony Liguori wrote:
>   
>> Michael S. Tsirkin wrote:
>>     
>>> Hi!
>>> pci bus reset does not seem to clear pci config registers, such as BAR
>>> registers, or memory space enable, of the attached devices: it only
>>> clears the interrupt state.
>>>
>>> This seems wrong, but easy to fix.
>>>   
>>>       
>> I don't think most pci devices reset their config space in their reset  
>> callbacks.
>>     
>
> For things like BAR registers, they really must.
>   

BARs should be registered via pci_register_bar so you should be able to 
centralize their reset.

> class codes are read only registers. Your proposal might be correct for
> some of these. But PCI registers that are reset, change as a result of
> guest activity, and reset values are typically specified by guest spec.
> So I don't think we should let users tweak these.
>   

Well, I guess my general point was that it would be good to add more 
structure to how config space is initialized.  I think a natural 
consequence of that is that it becomes easier to automatically fix the 
values on reset.

Regards,

Anthony Liguori