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charset="utf-8" From: Chenyi Qiang Modify memory_region_set_ram_discard_manager() to return -EBUSY if a RamDiscardManager is already set in the MemoryRegion. The caller must handle this failure, such as having virtio-mem undo its actions and fail the realize() process. Opportunistically move the call earlier to avoid complex error handling. This change is beneficial when introducing a new RamDiscardManager instance besides virtio-mem. After ram_block_coordinated_discard_require(true) unlocks all RamDiscardManager instances, only one instance is allowed to be set for one MemoryRegion at present. Suggested-by: David Hildenbrand Reviewed-by: David Hildenbrand Reviewed-by: Pankaj Gupta Tested-by: Alexey Kardashevskiy Reviewed-by: Alexey Kardashevskiy Reviewed-by: Xiaoyao Li Signed-off-by: Chenyi Qiang Link: https://lore.kernel.org/r/20250612082747.51539-3-chenyi.qiang@intel.c= om Signed-off-by: Peter Xu --- include/system/memory.h | 6 +++--- hw/virtio/virtio-mem.c | 30 +++++++++++++++++------------- system/memory.c | 10 +++++++--- 3 files changed, 27 insertions(+), 19 deletions(-) diff --git a/include/system/memory.h b/include/system/memory.h index da97753e28..60983d4977 100644 --- a/include/system/memory.h +++ b/include/system/memory.h @@ -2499,13 +2499,13 @@ static inline bool memory_region_has_ram_discard_ma= nager(MemoryRegion *mr) * * This function must not be called for a mapped #MemoryRegion, a #MemoryR= egion * that does not cover RAM, or a #MemoryRegion that already has a - * #RamDiscardManager assigned. + * #RamDiscardManager assigned. Return 0 if the rdm is set successfully. * * @mr: the #MemoryRegion * @rdm: #RamDiscardManager to set */ -void memory_region_set_ram_discard_manager(MemoryRegion *mr, - RamDiscardManager *rdm); +int memory_region_set_ram_discard_manager(MemoryRegion *mr, + RamDiscardManager *rdm); =20 /** * memory_region_find: translate an address/size relative to a diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index b3c126ea1e..2e491e8c44 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -1047,6 +1047,17 @@ static void virtio_mem_device_realize(DeviceState *d= ev, Error **errp) return; } =20 + /* + * Set ourselves as RamDiscardManager before the plug handler maps the + * memory region and exposes it via an address space. + */ + if (memory_region_set_ram_discard_manager(&vmem->memdev->mr, + RAM_DISCARD_MANAGER(vmem))) { + error_setg(errp, "Failed to set RamDiscardManager"); + ram_block_coordinated_discard_require(false); + return; + } + /* * We don't know at this point whether shared RAM is migrated using * QEMU or migrated using the file content. "x-ignore-shared" will be @@ -1061,6 +1072,7 @@ static void virtio_mem_device_realize(DeviceState *de= v, Error **errp) ret =3D ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb= )); if (ret) { error_setg_errno(errp, -ret, "Unexpected error discarding RAM"= ); + memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); ram_block_coordinated_discard_require(false); return; } @@ -1122,13 +1134,6 @@ static void virtio_mem_device_realize(DeviceState *d= ev, Error **errp) vmem->system_reset =3D VIRTIO_MEM_SYSTEM_RESET(obj); vmem->system_reset->vmem =3D vmem; qemu_register_resettable(obj); - - /* - * Set ourselves as RamDiscardManager before the plug handler maps the - * memory region and exposes it via an address space. - */ - memory_region_set_ram_discard_manager(&vmem->memdev->mr, - RAM_DISCARD_MANAGER(vmem)); } =20 static void virtio_mem_device_unrealize(DeviceState *dev) @@ -1136,12 +1141,6 @@ static void virtio_mem_device_unrealize(DeviceState = *dev) VirtIODevice *vdev =3D VIRTIO_DEVICE(dev); VirtIOMEM *vmem =3D VIRTIO_MEM(dev); =20 - /* - * The unplug handler unmapped the memory region, it cannot be - * found via an address space anymore. Unset ourselves. - */ - memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); - qemu_unregister_resettable(OBJECT(vmem->system_reset)); object_unref(OBJECT(vmem->system_reset)); =20 @@ -1154,6 +1153,11 @@ static void virtio_mem_device_unrealize(DeviceState = *dev) virtio_del_queue(vdev, 0); virtio_cleanup(vdev); g_free(vmem->bitmap); + /* + * The unplug handler unmapped the memory region, it cannot be + * found via an address space anymore. Unset ourselves. + */ + memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); ram_block_coordinated_discard_require(false); } =20 diff --git a/system/memory.c b/system/memory.c index 306e9ff9eb..d0c186e9f6 100644 --- a/system/memory.c +++ b/system/memory.c @@ -2106,12 +2106,16 @@ RamDiscardManager *memory_region_get_ram_discard_ma= nager(MemoryRegion *mr) return mr->rdm; } =20 -void memory_region_set_ram_discard_manager(MemoryRegion *mr, - RamDiscardManager *rdm) +int memory_region_set_ram_discard_manager(MemoryRegion *mr, + RamDiscardManager *rdm) { g_assert(memory_region_is_ram(mr)); - g_assert(!rdm || !mr->rdm); + if (mr->rdm && rdm) { + return -EBUSY; + } + mr->rdm =3D rdm; + return 0; } =20 uint64_t ram_discard_manager_get_min_granularity(const RamDiscardManager *= rdm, --=20 2.49.0