From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45679) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bKick-0006FI-Tu for qemu-devel@nongnu.org; Wed, 06 Jul 2016 04:56:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bKicg-0004KE-PK for qemu-devel@nongnu.org; Wed, 06 Jul 2016 04:56:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34247) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bKicg-0004Jx-Gy for qemu-devel@nongnu.org; Wed, 06 Jul 2016 04:55:58 -0400 Date: Wed, 6 Jul 2016 11:55:53 +0300 From: "Michael S. Tsirkin" Message-ID: <20160706111832-mutt-send-email-mst@redhat.com> References: <1467772593-29703-1-git-send-email-liang.z.li@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1467772593-29703-1-git-send-email-liang.z.li@intel.com> Subject: Re: [Qemu-devel] [PATCH v2] balloon: Fix failure of updating guest memory status List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Liang Li Cc: qemu-devel@nongnu.org, Ladi Prosek , Paolo Bonzini , dgilbert@redhat.com On Wed, Jul 06, 2016 at 10:36:33AM +0800, Liang Li wrote: > After live migration, 'guest-stats' can't get the expected memory > status in the guest. This issue is caused by commit 4eae2a657d. > The value of 's->stats_vq_elem' will be NULL after live migration, > and the check in the function 'balloon_stats_poll_cb()' will > prevent the 'virtio_notify()' from executing. So guest will not > update the memory status. > > Commit 4eae2a657d is doing the right thing, but 's->stats_vq_elem' > should be treated as part of balloon device state and migrated to > destination if it's not NULL to make everything works well. > > Signed-off-by: Liang Li > Suggested-by: Paolo Bonzini > Cc: Michael S. Tsirkin > Cc: Ladi Prosek > Cc: Paolo Bonzini I agree there's an issue but we don't change versions anymore. Breaking migrations for everyone is also not nice. How about queueing virtio_balloon_receive_stats so it will get invoked when vm starts? > --- > hw/virtio/virtio-balloon.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index 557d3f9..64e80c6 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -31,6 +31,7 @@ > #include "hw/virtio/virtio-access.h" > > #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT) > +#define BALLOON_VERSION 2 > > static void balloon_page(void *addr, int deflate) > { > @@ -404,15 +405,24 @@ static void virtio_balloon_save(QEMUFile *f, void *opaque) > static void virtio_balloon_save_device(VirtIODevice *vdev, QEMUFile *f) > { > VirtIOBalloon *s = VIRTIO_BALLOON(vdev); > + uint16_t elem_num = 0; > > qemu_put_be32(f, s->num_pages); > qemu_put_be32(f, s->actual); > + if (s->stats_vq_elem != NULL) { > + elem_num = 1; > + } > + qemu_put_be16(f, elem_num); > + if (elem_num) { > + qemu_put_virtqueue_element(f, s->stats_vq_elem); > + } > } > > static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id) > { > - if (version_id != 1) > + if (version_id < 1 || version_id > BALLOON_VERSION) { > return -EINVAL; > + } > > return virtio_load(VIRTIO_DEVICE(opaque), f, version_id); > } > @@ -421,9 +431,17 @@ static int virtio_balloon_load_device(VirtIODevice *vdev, QEMUFile *f, > int version_id) > { > VirtIOBalloon *s = VIRTIO_BALLOON(vdev); > + uint16_t elem_num = 0; > > s->num_pages = qemu_get_be32(f); > s->actual = qemu_get_be32(f); > + if (version_id == BALLOON_VERSION) { > + elem_num = qemu_get_be16(f); > + if (elem_num == 1) { > + s->stats_vq_elem = > + qemu_get_virtqueue_element(f, sizeof(VirtQueueElement)); > + } > + } > > if (balloon_stats_enabled(s)) { > balloon_stats_change_timer(s, s->stats_poll_interval); > @@ -455,7 +473,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) > > reset_stats(s); > > - register_savevm(dev, "virtio-balloon", -1, 1, > + register_savevm(dev, "virtio-balloon", -1, BALLOON_VERSION, > virtio_balloon_save, virtio_balloon_load, s); > } > > -- > 1.8.3.1