Re: qemu-kvm aborts - vhost_dev_unassign_memory: Assertion `to >= 0' failed.

Avi Kivity
2011-08-03T11:48:05Z

On 08/01/2011 08:44 PM, David Ahern wrote:
> qemu-kvm.git as of:
>
> commit dacdc4b10bafbb21120e1c24a9665444768ef999
> Merge: 7b69d4f 0af4922
> Author: Avi Kivity<avi@redhat.com>
> Date: Sun Jul 31 11:42:26 2011 +0300
>
> Merge branch 'upstream-merge' into next
>
> is aborting with the error:
>
> qemu-kvm: qemu-kvm.git/hw/vhost.c:123: vhost_dev_unassign_memory:
> Assertion `to>= 0' failed.
> Aborted
>

It's a bug in vhost:

/* Assign/unassign. Keep an unsorted array of non-overlapping
* memory regions in dev->mem. */
static void vhost_dev_unassign_memory(struct vhost_dev *dev,
uint64_t start_addr,
uint64_t size)
{
int from, to, n = dev->mem->nregions;
/* Track overlapping/split regions for sanity checking. */
int overlap_start = 0, overlap_end = 0, overlap_middle = 0, split = 0;

for (from = 0, to = 0; from < n; ++from, ++to) {
struct vhost_memory_region *reg = dev->mem->regions + to;
uint64_t reglast;
uint64_t memlast;
uint64_t change;

/* clone old region */
if (to != from) {
memcpy(reg, dev->mem->regions + from, sizeof *reg);
}

/* No overlap is simple */
if (!ranges_overlap(reg->guest_phys_addr, reg->memory_size,
start_addr, size)) {
continue;
}

/* Split only happens if supplied region
* is in the middle of an existing one. Thus it can not
* overlap with any other existing region. */
assert(!split);

reglast = range_get_last(reg->guest_phys_addr, reg->memory_size);
memlast = range_get_last(start_addr, size);

/* Remove whole region */
if (start_addr <= reg->guest_phys_addr && memlast >= reglast) {
--dev->mem->nregions;
--to;
assert(to >= 0);
++overlap_middle;
continue;
}

We're removing the first region, and 'to' goes negative. Michael?

--
error compiling committee.c: too many arguments to function