From a12ae584312347511a7a4fcd41800937658b657d Mon Sep 17 00:00:00 2001
From: "alex.lyn" <alex.lyn@antgroup.com>
Date: Thu, 17 Jul 2025 17:52:05 +0800
Subject: [PATCH] runtime-rs: Support hotplugging host block devices within
 qemu-rs

Although Previous implementation of hotplugging block device via QMP
can successfully hot-plug the regular file based block device, but it
fails when the backend is /dev/xxx(e.g. /dev/loop0). With analysis about
it, we can know that it lacks the ablility to hotplug host block devices.

This commit will fill the gap, and make it work well for host block
devices.

Signed-off-by: alex.lyn <alex.lyn@antgroup.com>
---
 .../crates/hypervisor/src/qemu/qmp.rs         | 75 ++++++++++++-------
 1 file changed, 46 insertions(+), 29 deletions(-)

diff --git a/src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs b/src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs
index e646402309..f6528303fe 100644
--- a/src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs
+++ b/src/runtime-rs/crates/hypervisor/src/qemu/qmp.rs
@@ -527,8 +527,51 @@ impl Qmp {
 
         // `blockdev-add`
         let node_name = format!("drive-{}", device_id);
+
+        let create_base_options = || qapi_qmp::BlockdevOptionsBase {
+            auto_read_only: None,
+            cache: if is_direct.is_none() {
+                None
+            } else {
+                Some(qapi_qmp::BlockdevCacheOptions {
+                    direct: is_direct,
+                    no_flush: None,
+                })
+            },
+            detect_zeroes: None,
+            discard: None,
+            force_share: None,
+            node_name: None,
+            read_only: Some(is_readonly),
+        };
+
+        let create_backend_options = || qapi_qmp::BlockdevOptionsFile {
+            aio: None,
+            aio_max_batch: None,
+            drop_cache: if !no_drop { None } else { Some(no_drop) },
+            locking: None,
+            pr_manager: None,
+            x_check_cache_dropped: None,
+            filename: path_on_host.to_owned(),
+        };
+
+        // Add block device backend and check if the file is a regular file or device
+        let blockdev_file = if std::fs::metadata(path_on_host)?.is_file() {
+            // Regular file
+            qmp::BlockdevOptions::file {
+                base: create_base_options(),
+                file: create_backend_options(),
+            }
+        } else {
+            // Host device (e.g., /dev/sdx, /dev/loopX)
+            qmp::BlockdevOptions::host_device {
+                base: create_base_options(),
+                host_device: create_backend_options(),
+            }
+        };
+
         self.qmp
-            .execute(&qmp::blockdev_add(qmp::BlockdevOptions::raw {
+            .execute(&qapi_qmp::blockdev_add(qmp::BlockdevOptions::raw {
                 base: qmp::BlockdevOptionsBase {
                     detect_zeroes: None,
                     cache: None,
@@ -540,39 +583,13 @@ impl Qmp {
                 },
                 raw: qmp::BlockdevOptionsRaw {
                     base: qmp::BlockdevOptionsGenericFormat {
-                        file: qmp::BlockdevRef::definition(Box::new(qmp::BlockdevOptions::file {
-                            base: qapi_qmp::BlockdevOptionsBase {
-                                auto_read_only: None,
-                                cache: if is_direct.is_none() {
-                                    None
-                                } else {
-                                    Some(qapi_qmp::BlockdevCacheOptions {
-                                        direct: is_direct,
-                                        no_flush: None,
-                                    })
-                                },
-                                detect_zeroes: None,
-                                discard: None,
-                                force_share: None,
-                                node_name: None,
-                                read_only: Some(is_readonly),
-                            },
-                            file: qapi_qmp::BlockdevOptionsFile {
-                                aio: None,
-                                aio_max_batch: None,
-                                drop_cache: if !no_drop { None } else { Some(no_drop) },
-                                locking: None,
-                                pr_manager: None,
-                                x_check_cache_dropped: None,
-                                filename: path_on_host.to_owned(),
-                            },
-                        })),
+                        file: qmp::BlockdevRef::definition(Box::new(blockdev_file)),
                     },
                     offset: None,
                     size: None,
                 },
             }))
-            .map_err(|e| anyhow!("blockdev_add {:?}", e))
+            .map_err(|e| anyhow!("blockdev_add backend {:?}", e))
             .map(|_| ())?;
 
         // `device_add`