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virtio-mem: Prepare for device unplug support

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In many cases, blindly unplugging a virtio-mem device is problematic. We
can only safely remove a device once:
* The guest is not expecting to be able to read unplugged memory
  (unplugged-inaccessible == on)
* The virtio-mem device does not have memory plugged (size == 0)
* The virtio-mem device does not have outstanding requests to the VM to
  plug memory (requested-size == 0)

So let's add a callback to the virtio-mem device class to check for that.
We'll wire-up virtio-mem-pci next.

Message-ID: <20230711153445.514112-7-david@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
This commit is contained in:
David Hildenbrand 2023-07-11 17:34:44 +02:00
parent aac44204bc
commit 92a8ee1b59
2 changed files with 26 additions and 0 deletions
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25
hw/virtio/virtio-mem.c
View File

@ -1512,6 +1512,30 @@ static void virtio_mem_rdm_unregister_listener(RamDiscardManager *rdm,
QLIST_REMOVE(rdl, next);
}
static void virtio_mem_unplug_request_check(VirtIOMEM *vmem, Error **errp)
{
if (vmem->unplugged_inaccessible == ON_OFF_AUTO_OFF) {
/*
* We could allow it with a usable region size of 0, but let's just
* not care about that legacy setting.
*/
error_setg(errp, "virtio-mem device cannot get unplugged while"
" '" VIRTIO_MEM_UNPLUGGED_INACCESSIBLE_PROP "' != 'on'");
return;
}
if (vmem->size) {
error_setg(errp, "virtio-mem device cannot get unplugged while"
" '" VIRTIO_MEM_SIZE_PROP "' != '0'");
return;
}
if (vmem->requested_size) {
error_setg(errp, "virtio-mem device cannot get unplugged while"
" '" VIRTIO_MEM_REQUESTED_SIZE_PROP "' != '0'");
return;
}
}
static void virtio_mem_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
@ -1534,6 +1558,7 @@ static void virtio_mem_class_init(ObjectClass *klass, void *data)
vmc->get_memory_region = virtio_mem_get_memory_region;
vmc->add_size_change_notifier = virtio_mem_add_size_change_notifier;
vmc->remove_size_change_notifier = virtio_mem_remove_size_change_notifier;
vmc->unplug_request_check = virtio_mem_unplug_request_check;
rdmc->get_min_granularity = virtio_mem_rdm_get_min_granularity;
rdmc->is_populated = virtio_mem_rdm_is_populated;

1
include/hw/virtio/virtio-mem.h
View File

@ -98,6 +98,7 @@ struct VirtIOMEMClass {
MemoryRegion *(*get_memory_region)(VirtIOMEM *vmem, Error **errp);
void (*add_size_change_notifier)(VirtIOMEM *vmem, Notifier *notifier);
void (*remove_size_change_notifier)(VirtIOMEM *vmem, Notifier *notifier);
void (*unplug_request_check)(VirtIOMEM *vmem, Error **errp);
};
#endif