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Date: Tue, 09 Mar 2010 11:34:44 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH] Inter-VM shared memory PCI device
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To: Avi Kivity <avi@redhat.com>
Cc: Cam Macdonell <cam@cs.ualberta.ca>, qemu-devel@nongnu.org, kvm@vger.kernel.org

On 03/09/2010 11:28 AM, Avi Kivity wrote:
> On 03/09/2010 05:27 PM, Cam Macdonell wrote:
>>
>>>
>>>>   Registers are used
>>>> for synchronization between guests sharing the same memory object when
>>>> interrupts are supported (this requires using the shared memory 
>>>> server).
>>>>
>>> How does the driver detect whether interrupts are supported or not?
>> At the moment, the VM ID is set to -1 if interrupts aren't supported,
>> but that may not be the clearest way to do things.  With UIO is there
>> a way to detect if the interrupt pin is on?
>
> I suggest not designing the device to uio.  Make it a good 
> guest-independent device, and if uio doesn't fit it, change it.

You can always fall back to reading the config space directly.  It's not 
strictly required that you stick to the UIO interface.

> Why not support interrupts unconditionally?  Is the device useful 
> without interrupts?

You can always just have interrupts enabled and not use them if that's 
desired.

Regards,

Anthony Liguori