Re: [Query] [GUEST PAGE HINTING] How to handle virtqueue_kick from the guest in QEMU

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Aug 11, 2017 at 05:00:15PM -0400, Nitesh Narayan Lal wrote:
> Hi,
> 
> In my project of "Guest Page Hinting"[1], I have a list of pages which
> are supposed to be passed to the host. Now I am trying to figure out the
> changes which I should make in QEMU in order to pass this request to the
> host.
> 
> Unlike virtio balloon where the request to deflate/inflate is derived
> from the host, in my case, I need to figure out how the request which is
> generated in the guest could be received in QEMU. One way to go about
> this is to have my own function pointer pointing a to a function
> qemu_page_hinting() in virtio-balloon.c under QEMU. Now the part where I
> am not sure is how exactly I will ensure that when virtqueue_kick
> arrives in QEMU this function is invoked. (I am planning to use the same
> deflate_vq for my use-case).
>
> Another way could be to make changes in the existing
> "virtio_balloon_handle_output" and may add another flag in the virtqueue
> structure using which I could distinguish if it's a guest page hinting
> request. But even in this case, I am not sure how will it work because
> from what I understood when a user sends a deflate request then this
> function gets invoked and after all the processing it notifies the
> guest. (Which is opposite of what I am trying to achieve).
> 
> Any suggestion what should be the right way to go forward?
> 
> [1] https://www.spinics.net/lists/kvm/msg153666.html


I would just create a new vq for this, at least initially.


> -- 
> 
> Regards
> Nitesh
>