Re: [Qemu-devel] [virtio-dev] Re: [PATCH v4 3/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT

[Michael S. Tsirkin]

On Wed, Mar 14, 2018 at 10:43:01AM +0800, Wei Wang wrote:
> On 03/14/2018 12:49 AM, Michael S. Tsirkin wrote:
> > On Wed, Mar 07, 2018 at 08:34:24PM +0800, Wei Wang wrote:
> > 
> > > Signed-off-by: Wei Wang <address@hidden>
> > > Signed-off-by: Liang Li <address@hidden>
> > > CC: Michael S. Tsirkin <address@hidden>
> > > CC: Dr. David Alan Gilbert <address@hidden>
> > > CC: Juan Quintela <address@hidden>
> > I find it suspicious that neither unrealize nor reset
> > functions have been touched at all.
> > Are you sure you have thought through scenarious like
> > hot-unplug or disabling the device by guest?
> 
> OK. I think we can call balloon_free_page_stop in unrealize and reset.
> 
> 
> > +static void *virtio_balloon_poll_free_page_hints(void *opaque)
> > +{
> > +    VirtQueueElement *elem;
> > +    VirtIOBalloon *dev = opaque;
> > +    VirtQueue *vq = dev->free_page_vq;
> > +    uint32_t id;
> > +    size_t size;
> > What makes it safe to poke at this device from multiple threads?
> > I think that it would be safer to do it from e.g. BH.
> > 
> 
> Actually the free_page_optimization thread is the only user of free_page_vq,
> and there is only one optimization thread each time. Would this be safe
> enough?
> 
> Best,
> Wei

Aren't there other fields there? Also things like reset affect all VQs.

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MST