From ee6398d862c108f8136a26d93d26680f3d222a3a Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 26 Sep 2023 20:57:38 +0200 Subject: [PATCH] virtio-mem: Mark memslot alias memory regions unmergeable MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Let's mark the memslot alias memory regions as unmergable, such that flatview and vhost won't merge adjacent memory region aliases and we can atomically map/unmap individual aliases without affecting adjacent alias memory regions. This handles vhost and vfio in multiple-memslot mode correctly (which do not support atomic memslot updates) and avoids the temporary removal of large memslots, which can be an expensive operation. For example, vfio might have to unpin + repin a lot of memory, which is undesired. Message-ID: <20230926185738.277351-19-david@redhat.com> Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Michael S. Tsirkin Signed-off-by: David Hildenbrand --- hw/virtio/virtio-mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index e1e4250e69..9dc3c61b5a 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -940,6 +940,12 @@ static void virtio_mem_prepare_memslots(VirtIOMEM *vmem) memory_region_init_alias(&vmem->memslots[idx], OBJECT(vmem), name, &vmem->memdev->mr, memslot_offset, memslot_size); + /* + * We want to be able to atomically and efficiently activate/deactivate + * individual memslots without affecting adjacent memslots in memory + * notifiers. + */ + memory_region_set_unmergeable(&vmem->memslots[idx], true); } } -- 2.11.0