[Qemu-devel] Re: [PATCH v5 4/5] Inter-VM shared memory PCI device

[Cam Macdonell]

On Mon, May 10, 2010 at 10:40 AM, Avi Kivity <address@hidden> wrote:
> On 05/10/2010 06:41 PM, Cam Macdonell wrote:
>>
>>> What would happen to any data written to the BAR before the the handshake
>>> completed?  I think it would disappear.
>>>
>>
>> But, the BAR isn't there until the handshake is completed.  Only after
>> receiving the shared memory fd does my device call pci_register_bar()
>> in the callback function.  So there may be a case with BAR2 (the
>> shared memory BAR) missing during initialization.  FWIW, I haven't
>> encountered this.
>>
>
> Well, that violates PCI.  You can't have a PCI device with no BAR, then have
> a BAR appear.  It may work since the BAR is registered a lot faster than the
> BIOS is able to peek at it, but it's a race nevertheless.

Agreed.  I'll get Anthony's idea up and running.  It seems that is the
way forward.

Cam