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virtio-mem: Fail if a memory backend with "prealloc=on" is specified

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"prealloc=on" for the memory backend does not work as expected, as
virtio-mem will simply discard all preallocated memory immediately again.
In the best case, it's an expensive NOP. In the worst case, it's an
unexpected allocation error.

Instead, "prealloc=on" should be specified for the virtio-mem device only,
such that virtio-mem will try preallocating memory before plugging
memory dynamically to the guest. Fail if such a memory backend is
provided.

Tested-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>S
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
David Hildenbrand 2023-01-17 12:22:47 +01:00 committed by Juan Quintela
parent 80fe315c38
commit ce1761f0f9
1 changed files with 6 additions and 0 deletions
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6
hw/virtio/virtio-mem.c
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@ -772,6 +772,12 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp)
error_setg(errp, "'%s' property specifies an unsupported memdev",
VIRTIO_MEM_MEMDEV_PROP);
return;
} else if (vmem->memdev->prealloc) {
error_setg(errp, "'%s' property specifies a memdev with preallocation"
" enabled: %s. Instead, specify 'prealloc=on' for the"
" virtio-mem device. ", VIRTIO_MEM_MEMDEV_PROP,
object_get_canonical_path_component(OBJECT(vmem->memdev)));
return;
}
if ((nb_numa_nodes && vmem->node >= nb_numa_nodes) ||