From 874adf45dbfbae2810423527d777ba37bc5ca974 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 22 Feb 2017 16:37:34 +0000 Subject: [PATCH] virtio: add missing region cache init in virtio_load() Commit 97cd965c070152bc626c7507df9fb356bbe1cd81 ("virtio: use VRingMemoryRegionCaches for avail and used rings") switched to a memory region cache to avoid repeated map/unmap operations. The virtio_load() process is a little tricky because vring addresses are serialized in two separate places. VIRTIO 1.0 devices serialize desc and then a subsection with used and avail. Legacy devices only serialize desc. Live migration of VIRTIO 1.0 devices fails on the destination host with: VQ 0 size 0x80 < last_avail_idx 0x12f8 - used_idx 0x0 Failed to load virtio-blk:virtio error while loading state for instance 0x0 of device '0000:00:04.0/virtio-blk' This happens because the memory region cache is only initialized after desc is loaded and not after the used and avail subsection is loaded. If the guest chose memory addresses that don't match the legacy ring layout then the wrong guest memory location is accessed. Wait until all ring addresses are known before trying to initialize the region cache. Also clarify the incomplete comment about VIRTIO-1 ring address subsection. Cc: Dr. David Alan Gilbert Cc: Paolo Bonzini Signed-off-by: Stefan Hajnoczi Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck Tested-by: Eric Auger --- hw/virtio/virtio.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 294c909cce..efce4b343a 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -1857,7 +1857,10 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f) if (k->has_variable_vring_alignment) { qemu_put_be32(f, vdev->vq[i].vring.align); } - /* XXX virtio-1 devices */ + /* + * Save desc now, the rest of the ring addresses are saved in + * subsections for VIRTIO-1 devices. + */ qemu_put_be64(f, vdev->vq[i].vring.desc); qemu_put_be16s(f, &vdev->vq[i].last_avail_idx); if (k->save_queue) { @@ -1998,14 +2001,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) vdev->vq[i].signalled_used_valid = false; vdev->vq[i].notification = true; - if (vdev->vq[i].vring.desc) { - /* XXX virtio-1 devices */ - virtio_queue_update_rings(vdev, i); - } else if (vdev->vq[i].last_avail_idx) { + if (!vdev->vq[i].vring.desc && vdev->vq[i].last_avail_idx) { error_report("VQ %d address 0x0 " "inconsistent with Host index 0x%x", i, vdev->vq[i].last_avail_idx); - return -1; + return -1; } if (k->load_queue) { ret = k->load_queue(qbus->parent, i, f); @@ -2066,6 +2066,19 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) for (i = 0; i < num; i++) { if (vdev->vq[i].vring.desc) { uint16_t nheads; + + /* + * VIRTIO-1 devices migrate desc, used, and avail ring addresses so + * only the region cache needs to be set up. Legacy devices need + * to calculate used and avail ring addresses based on the desc + * address. + */ + if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { + virtio_init_region_cache(vdev, i); + } else { + virtio_queue_update_rings(vdev, i); + } + nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx; /* Check it isn't doing strange things with descriptor numbers. */ if (nheads > vdev->vq[i].vring.num) { -- 2.39.2