Re: [Qemu-devel] [PATCH] vhost-net: Move asserts to after check for end < start

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Mar 30, 2012 at 07:21:22PM -0700, Josh Durgin wrote:
> On 12/16/2011 12:33 PM, Bruce Rogers wrote:
> >When migrating a vm using vhost-net we hit the following assertion:
> >
> >qemu-kvm: /usr/src/packages/BUILD/qemu-kvm-0.15.1/hw/vhost.c:30:
> >vhost_dev_sync_region: Assertion `start / (0x1000 * (8 *
> >sizeof(vhost_log_chunk_t)))<  dev->log_size' failed.
> 
> I consistently hit this assert while testing live migration with
> qemu 1.0.1 and the master branch. Applying this patch allowed live
> migration to complete successfully. Maybe it could be reviewed and
> merged?

Yes, thanks for the reminder. I've applied a patch by Alex Williamson that
addresses this and other crashes.

> >The cases which the end<  start check is intended to catch, such as
> >for vga video memory, will also likely trigger the assertion.
> >Reorder the code to handle this correctly.
> >
> >Signed-off-by: Bruce Rogers<brogers@suse.com>
> >---
> >  hw/vhost.c |    4 ++--
> >  1 files changed, 2 insertions(+), 2 deletions(-)
> >
> >diff --git a/hw/vhost.c b/hw/vhost.c
> >index 0870cb7..7309f71 100644
> >--- a/hw/vhost.c
> >+++ b/hw/vhost.c
> >@@ -26,11 +26,11 @@ static void vhost_dev_sync_region(struct vhost_dev *dev,
> >      vhost_log_chunk_t *to = dev->log + end / VHOST_LOG_CHUNK + 1;
> >      uint64_t addr = (start / VHOST_LOG_CHUNK) * VHOST_LOG_CHUNK;
> >
> >-    assert(end / VHOST_LOG_CHUNK<  dev->log_size);
> >-    assert(start / VHOST_LOG_CHUNK<  dev->log_size);
> >      if (end<  start) {
> >          return;
> >      }
> >+    assert(end / VHOST_LOG_CHUNK<  dev->log_size);
> >+    assert(start / VHOST_LOG_CHUNK<  dev->log_size);
> >      for (;from<  to; ++from) {
> >          vhost_log_chunk_t log;
> >          int bit;