Re: R/W HG memory mappings with kvm?

[Cam Macdonell <cam@cs.ualberta.ca>]

On 8-Jul-09, at 4:01 PM, Stephen Donnelly wrote:

> On Thu, Jul 9, 2009 at 9:45 AM, Cam Macdonell<cam@cs.ualberta.ca>  
> wrote:
>> Hi Stephen,
>>
>> Here is the latest patch that supports interrupts.  I am currently  
>> working
>> on a broadcast mechanism that should be ready fairly soon.
>>
>> http://patchwork.kernel.org/patch/22368/
>>
>> I have some test scripts that can demonstrate how to use the memory  
>> between
>> guest/host and guest/guest.  Let me know if you would like me to  
>> send them
>> to you.
>
> Hi Cam,
>
> Thanks for the pointer. That makes perfect sense, I'm familiar with
> PCI drivers so that's fine.
>
> Is there a corresponding qemu patch for the backend to the guest pci
> driver?

Oops right.   For some reason I can't my driver patch in patchwork.

http://kerneltrap.org/mailarchive/linux-kvm/2009/5/7/5665734

> I'm curious how the buffer memory is allocated and how BAR
> accesses are handled from the host side.

The memory for the device allocated as a POSIX shared memory object  
and then mmapped on to the allocated BAR region in Qemu's allocated  
memory.  That's actually one spot that needs a bit of fixing by  
passing the already allocated memory object to qemu instead of  
mmapping on to it.

Cam



-----------------------------------------------
A. Cameron Macdonell
Ph.D. Student
Department of Computing Science
University of Alberta
cam@cs.ualberta.ca