{"id":2221323,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2221323/?format=json","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.0/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260409070114.11313-3-matthieu@min.io>","date":"2026-04-09T07:01:11","name":"[2/2] block/monitor: add drive_insert HMP command","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"b469248ea1bc7826219e603869ffe3c67c6223e6","submitter":{"id":93098,"url":"http://patchwork.ozlabs.org/api/1.0/people/93098/?format=json","name":"mr-083","email":"matthieu@minio.io"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260409070114.11313-3-matthieu@min.io/mbox/","series":[{"id":499254,"url":"http://patchwork.ozlabs.org/api/1.0/series/499254/?format=json","date":"2026-04-09T07:01:10","name":"NVMe namespace hotplug and drive reconnection support","version":1,"mbox":"http://patchwork.ozlabs.org/series/499254/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2221323/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=minio.io header.i=@minio.io header.a=rsa-sha256\n header.s=minio header.b=ri/Wtg3M;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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helo=mail-wm1-x330.google.com","X-Spam_score_int":"-10","X-Spam_score":"-1.1","X-Spam_bar":"-","X-Spam_report":"(-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n HK_NAME_MR_MRS=0.998,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=no autolearn_force=no","X-Spam_action":"no action","X-Mailman-Approved-At":"Thu, 09 Apr 2026 04:19:30 -0400","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Add a drive_insert HMP command that reconnects a host block device file\nto an existing guest device whose backing store was previously removed\nwith drive_del.\n\nAfter drive_del, the BlockBackend remains attached to the guest device\nbut has no BlockDriverState (shown as \"[not inserted]\" in info block).\ndrive_insert opens the specified file, finds the device's BlockBackend\nby iterating all backends and matching the attached device ID, then\ncalls blk_insert_bs() to reconnect the backing store.\n\nThis complements drive_del for non-removable devices (such as NVMe\nnamespaces) where blockdev-change-medium cannot be used. Combined with\nPCIe AER Surprise Down error injection to trigger a controller reset,\nthis enables complete NVMe disk hot-swap simulation where the guest\nsees the same device names throughout.\n\nExample usage:\n drive_del drv0 # remove backing store\n drive_insert ns0 disk.qcow2 # reconnect backing\n pcie_aer_inject_error rp0 SDN # trigger controller reset\n\nSigned-off-by: Matthieu Receveur \n---\n block/monitor/block-hmp-cmds.c | 59 ++++++++++++++++++++++++++++++++++\n hmp-commands.hx | 18 +++++++++++\n include/block/block-hmp-cmds.h | 1 +\n 3 files changed, 78 insertions(+)","diff":"diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c\nindex 1fd28d59eb..77e9662ead 100644\n--- a/block/monitor/block-hmp-cmds.c\n+++ b/block/monitor/block-hmp-cmds.c\n@@ -38,7 +38,9 @@\n #include \"qemu/osdep.h\"\n #include \"hw/core/boards.h\"\n #include \"system/block-backend.h\"\n+#include \"system/block-backend-global-state.h\"\n #include \"system/blockdev.h\"\n+#include \"block/block-global-state.h\"\n #include \"qapi/qapi-commands-block.h\"\n #include \"qapi/qapi-commands-block-export.h\"\n #include \"qobject/qdict.h\"\n@@ -195,6 +197,63 @@ unlock:\n hmp_handle_error(mon, err);\n }\n \n+void hmp_drive_insert(Monitor *mon, const QDict *qdict)\n+{\n+ const char *id = qdict_get_str(qdict, \"id\");\n+ const char *filename = qdict_get_str(qdict, \"filename\");\n+ BlockBackend *blk = NULL;\n+ BlockBackend *iter;\n+ BlockDriverState *bs;\n+ Error *err = NULL;\n+\n+ GLOBAL_STATE_CODE();\n+\n+ /*\n+ * After drive_del, the BlockBackend is removed from the monitor name\n+ * registry but still attached to the device. Find it by iterating all\n+ * BlockBackends and matching by the device ID shown in \"info block\".\n+ */\n+ for (iter = blk_all_next(NULL); iter; iter = blk_all_next(iter)) {\n+ DeviceState *dev = blk_get_attached_dev(iter);\n+ if (dev && dev->id && strcmp(dev->id, id) == 0) {\n+ blk = iter;\n+ break;\n+ }\n+ }\n+\n+ if (!blk) {\n+ /* Fallback: try by block backend name */\n+ blk = blk_by_name(id);\n+ }\n+\n+ if (!blk) {\n+ error_setg(&err, \"Device '%s' not found\", id);\n+ goto out;\n+ }\n+\n+ if (blk_bs(blk)) {\n+ error_setg(&err, \"Device '%s' already has a medium inserted\", id);\n+ goto out;\n+ }\n+\n+ bs = bdrv_open(filename, NULL, NULL, BDRV_O_RDWR, &err);\n+ if (!bs) {\n+ goto out;\n+ }\n+\n+ if (blk_insert_bs(blk, bs, &err) < 0) {\n+ bdrv_unref(bs);\n+ goto out;\n+ }\n+\n+ bdrv_unref(bs);\n+ monitor_printf(mon, \"OK\\n\");\n+ return;\n+\n+out:\n+ hmp_handle_error(mon, err);\n+}\n+\n void hmp_commit(Monitor *mon, const QDict *qdict)\n {\n const char *device = qdict_get_str(qdict, \"device\");\ndiff --git a/hmp-commands.hx b/hmp-commands.hx\nindex 5cc4788f12..79af8e8988 100644\n--- a/hmp-commands.hx\n+++ b/hmp-commands.hx\n@@ -207,6 +207,24 @@ SRST\n actions (drive options rerror, werror).\n ERST\n \n+ {\n+ .name = \"drive_insert\",\n+ .args_type = \"id:B,filename:F\",\n+ .params = \"device filename\",\n+ .help = \"insert a host block device into an empty drive\",\n+ .cmd = hmp_drive_insert,\n+ },\n+\n+SRST\n+``drive_insert`` *device* *filename*\n+ Insert a host block device file into a drive that has been emptied by\n+ ``drive_del``. This reconnects the backing store without removing the\n+ guest device, enabling transparent disk hot-swap for non-removable devices\n+ such as NVMe namespaces. Combined with PCIe AER Surprise Down error\n+ injection (``pcie_aer_inject_error`` *device* ``SDN``), this enables\n+ complete NVMe disk hot-swap simulation.\n+ERST\n+\n {\n .name = \"change\",\n .args_type = \"device:B,force:-f,target:F,arg:s?,read-only-mode:s?\",\ndiff --git a/include/block/block-hmp-cmds.h b/include/block/block-hmp-cmds.h\nindex 71113cd7ef..73c9607402 100644\n--- a/include/block/block-hmp-cmds.h\n+++ b/include/block/block-hmp-cmds.h\n@@ -21,6 +21,7 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict);\n \n void hmp_commit(Monitor *mon, const QDict *qdict);\n void hmp_drive_del(Monitor *mon, const QDict *qdict);\n+void hmp_drive_insert(Monitor *mon, const QDict *qdict);\n \n void hmp_drive_mirror(Monitor *mon, const QDict *qdict);\n void hmp_drive_backup(Monitor *mon, const QDict *qdict);\n","prefixes":["2/2"]}