From 92a8ee1b594244a82d4c955eab907034f8953f8b Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 11 Jul 2023 17:34:44 +0200 Subject: [PATCH] virtio-mem: Prepare for device unplug support 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 Reviewed-by: Michael S. Tsirkin Signed-off-by: David Hildenbrand --- hw/virtio/virtio-mem.c | 25 +++++++++++++++++++++++++ include/hw/virtio/virtio-mem.h | 1 + 2 files changed, 26 insertions(+) diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index 3f41e00e74..b6e781741e 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -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; diff --git a/include/hw/virtio/virtio-mem.h b/include/hw/virtio/virtio-mem.h index f15e561785..ab0fe2b4f2 100644 --- a/include/hw/virtio/virtio-mem.h +++ b/include/hw/virtio/virtio-mem.h @@ -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