From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 05/21] virtio: modify save/load handler to handle inuse varialble. Date: Sun, 28 Nov 2010 11:28:57 +0200 Message-ID: <20101128092857.GA3342@redhat.com> References: <1290665220-26478-1-git-send-email-tamura.yoshiaki@lab.ntt.co.jp> <1290665220-26478-6-git-send-email-tamura.yoshiaki@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org, avi@redhat.com, anthony@codemonkey.ws, aliguori@us.ibm.com, mtosatti@redhat.com, dlaor@redhat.com, ananth@in.ibm.com, psuriset@linux.vnet.ibm.com, vatsa@linux.vnet.ibm.com, stefanha@linux.vnet.ibm.com, ohmura.kei@lab.ntt.co.jp To: Yoshiaki Tamura Return-path: Received: from mx1.redhat.com ([209.132.183.28]:60130 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751797Ab0K1J35 (ORCPT ); Sun, 28 Nov 2010 04:29:57 -0500 Content-Disposition: inline In-Reply-To: <1290665220-26478-6-git-send-email-tamura.yoshiaki@lab.ntt.co.jp> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Nov 25, 2010 at 03:06:44PM +0900, Yoshiaki Tamura wrote: > Modify inuse type to uint16_t, let save/load to handle, and revert > last_avail_idx with inuse if there are outstanding emulation. > > Signed-off-by: Yoshiaki Tamura This changes migration format, so it will break compatibility with existing drivers. More generally, I think migrating internal state that is not guest visible is always a mistake as it ties migration format to an internal implementation (yes, I know we do this sometimes, but we should at least try not to add such cases). I think the right thing to do in this case is to flush outstanding work when vm is stopped. Then, we are guaranteed that inuse is 0. I sent patches that do this for virtio net and block. > --- > hw/virtio.c | 8 +++++++- > 1 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/hw/virtio.c b/hw/virtio.c > index 849a60f..5509644 100644 > --- a/hw/virtio.c > +++ b/hw/virtio.c > @@ -72,7 +72,7 @@ struct VirtQueue > VRing vring; > target_phys_addr_t pa; > uint16_t last_avail_idx; > - int inuse; > + uint16_t inuse; > uint16_t vector; > void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq); > VirtIODevice *vdev; > @@ -671,6 +671,7 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f) > qemu_put_be32(f, vdev->vq[i].vring.num); > qemu_put_be64(f, vdev->vq[i].pa); > qemu_put_be16s(f, &vdev->vq[i].last_avail_idx); > + qemu_put_be16s(f, &vdev->vq[i].inuse); > if (vdev->binding->save_queue) > vdev->binding->save_queue(vdev->binding_opaque, i, f); > } > @@ -711,6 +712,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f) > vdev->vq[i].vring.num = qemu_get_be32(f); > vdev->vq[i].pa = qemu_get_be64(f); > qemu_get_be16s(f, &vdev->vq[i].last_avail_idx); > + qemu_get_be16s(f, &vdev->vq[i].inuse); > + > + /* revert last_avail_idx if there are outstanding emulation. */ > + vdev->vq[i].last_avail_idx -= vdev->vq[i].inuse; > + vdev->vq[i].inuse = 0; > > if (vdev->vq[i].pa) { > virtqueue_init(&vdev->vq[i]); > -- > 1.7.1.2 > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html