Re: R/W HG memory mappings with kvm?

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

Stephen Donnelly wrote:
> On Thu, Jul 9, 2009 at 6:01 PM, Cam Macdonell<cam@cs.ualberta.ca> wrote:
> 
>>> 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
> 
> Thanks for the link, I have read through the thread now. It seems very
> relevant to what I am doing. Have you found a link to your qemu-kvm
> backend patches? Or are you running your own git tree? I don't really
> know where to look.

Oops, I realize now that I passed the driver patch both times.  Here is 
the old patch.

http://patchwork.kernel.org/patch/22363/

What are you compiling against?  the git tree or a particular version? 
The above patch won't compile against the latest git tree due to changes 
to how BARs are setup in Qemu.  I can send you a patch for the latest 
tree if you need it.

Cam

> 
>>> 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.
> 
> Right, I would be passing the memory in pre-allocated as well, but
> should be a relatively simple change.
> 
> Regards,
> Stephen.