On Wed, Nov 24, 2021 at 03:58:22PM +0800, Jason Wang wrote: > On Wed, Nov 24, 2021 at 3:03 PM Michael S. Tsirkin <m...@redhat.com> wrote: > > > > On Wed, Nov 24, 2021 at 12:32:55PM +0800, Jason Wang wrote: > > > Spec said: > > > > > > "and len the total of bytes written into the buffer." > > > > > > For inflateq, deflateq and statsq, we don't process in_sg so the used > > > length should be zero. For free_page_vq, though the free pages are > > > supplied via in_sgs, zero used length should still be fine since > > > anyway driver is expected to use the length in this case and it > > > simplifies the error handling path. > > > > > > Signed-off-by: Jason Wang <jasow...@redhat.com> > > > > I think for free page vq the point is that the pages are > > zeroed by hypervisor, so we must set used len accordingly. No? > > I may miss something, I think it is used for clearing the dirty > bitmaps to avoid migrating unused pages, the zeroing is not needed. > > Thanks
And, once the page is migrated, it's value on destination may differ from one on source. > > > > > --- > > > hw/virtio/virtio-balloon.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > > > index c6962fcbfe..3e52daa793 100644 > > > --- a/hw/virtio/virtio-balloon.c > > > +++ b/hw/virtio/virtio-balloon.c > > > @@ -231,7 +231,7 @@ static void balloon_stats_poll_cb(void *opaque) > > > return; > > > } > > > > > > - virtqueue_push(s->svq, s->stats_vq_elem, s->stats_vq_offset); > > > + virtqueue_push(s->svq, s->stats_vq_elem, 0); > > > virtio_notify(vdev, s->svq); > > > g_free(s->stats_vq_elem); > > > s->stats_vq_elem = NULL; > > > @@ -438,7 +438,7 @@ static void virtio_balloon_handle_output(VirtIODevice > > > *vdev, VirtQueue *vq) > > > memory_region_unref(section.mr); > > > } > > > > > > - virtqueue_push(vq, elem, offset); > > > + virtqueue_push(vq, elem, 0); > > > virtio_notify(vdev, vq); > > > g_free(elem); > > > virtio_balloon_pbp_free(&pbp); > > > @@ -549,7 +549,7 @@ static bool get_free_page_hints(VirtIOBalloon *dev) > > > } > > > > > > out: > > > - virtqueue_push(vq, elem, 1); > > > + virtqueue_push(vq, elem, 0); > > > g_free(elem); > > > return ret; > > > } > > > -- > > > 2.25.1 > >
