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[PATCH v2] ui/vdagent: add migration blocker when machine version < 10.1

Fiona Ebner posted 1 patch 1 month ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20260310142552.240877-1-f.ebner@proxmox.com
Maintainers: Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>
hw/core/machine.c |  1 +
ui/vdagent.c      | 46 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)
[PATCH v2] ui/vdagent: add migration blocker when machine version < 10.1
Posted by Fiona Ebner 1 month ago 
In QEMU 10.1, commit 5d56bff11e ("ui/vdagent: add migration support")
added migration support for the vdagent chardev and commit 42000e0013
("ui/vdagent: remove migration blocker") removed the migration
blocker. No compat for older machine versions was added, so migration
with pre-10.1 machine version, from a 10.1 binary to a pre-10.1 binary
will result in a failure when loading the VM state in the target
instance:

> Unknown savevm section or instance 'vdagent' 0. Make sure that your
> current VM setup matches your saved VM setup, including any
> hotplugged devices

Add a compat flag to block migration when the machine version is less
than 10.1 to avoid this.

Cc: qemu-stable@nongnu.org
Fixes: 42000e0013 ("ui/vdagent: remove migration blocker")
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---

Changes in v2:
* rebase on current master, adapting to commit 8c84f31ace
  ("chardev: .chr_open(): add boolean return value")

 hw/core/machine.c |  1 +
 ui/vdagent.c      | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index a14ad05b9a..6cf0e2f404 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -57,6 +57,7 @@ GlobalProperty hw_compat_10_0[] = {
     { "vfio-pci", "x-migration-load-config-after-iter", "off" },
     { "ramfb", "use-legacy-x86-rom", "true"},
     { "vfio-pci-nohotplug", "use-legacy-x86-rom", "true" },
+    { "chardev-qemu-vdagent", "x-migration-blocked", "true" },
 };
 const size_t hw_compat_10_0_len = G_N_ELEMENTS(hw_compat_10_0);
 
diff --git a/ui/vdagent.c b/ui/vdagent.c
index 5a5e4bf681..bb0c4aa14c 100644
--- a/ui/vdagent.c
+++ b/ui/vdagent.c
@@ -6,6 +6,8 @@
 #include "qemu/option.h"
 #include "qemu/units.h"
 #include "hw/core/qdev.h"
+#include "hw/core/qdev-properties.h"
+#include "migration/blocker.h"
 #include "ui/clipboard.h"
 #include "ui/console.h"
 #include "ui/input.h"
@@ -24,6 +26,10 @@
 struct VDAgentChardev {
     Chardev parent;
 
+    /* needed for machine versions < 10.1 when migration was not supported */
+    Error *migration_blocker;
+    bool migration_blocked;
+
     /* config */
     bool mouse;
     bool clipboard;
@@ -657,6 +663,12 @@ static bool vdagent_chr_open(Chardev *chr, ChardevBackend *backend,
     return false;
 #endif
 
+    if (vd->migration_blocked) {
+        if (migrate_add_blocker(&vd->migration_blocker, errp) != 0) {
+            return false;
+        }
+    }
+
     vd->mouse = VDAGENT_MOUSE_DEFAULT;
     if (cfg->has_mouse) {
         vd->mouse = cfg->mouse;
@@ -901,6 +913,19 @@ static void vdagent_chr_parse(QemuOpts *opts, ChardevBackend *backend,
 
 /* ------------------------------------------------------------------ */
 
+static bool get_migration_blocked(Object *o, Error **errp)
+{
+    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(o);
+    return vd->migration_blocked;
+}
+
+static void set_migration_blocked(Object *o, bool migration_blocked,
+                                   Error **errp)
+{
+    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(o);
+    vd->migration_blocked = migration_blocked;
+}
+
 static void vdagent_chr_class_init(ObjectClass *oc, const void *data)
 {
     ChardevClass *cc = CHARDEV_CLASS(oc);
@@ -910,6 +935,10 @@ static void vdagent_chr_class_init(ObjectClass *oc, const void *data)
     cc->chr_write        = vdagent_chr_write;
     cc->chr_set_fe_open  = vdagent_chr_set_fe_open;
     cc->chr_accept_input = vdagent_chr_accept_input;
+
+    object_class_property_add_bool(oc, "x-migration-blocked",
+                                   get_migration_blocked,
+                                   set_migration_blocked);
 }
 
 static int post_load(void *opaque, int version_id)
@@ -1064,10 +1093,26 @@ static void vdagent_chr_instance_init(Object *obj)
     vmstate_register_any(NULL, &vmstate_vdagent, vd);
 }
 
+static void vdagent_post_init(Object *obj)
+{
+    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
+
+    object_apply_compat_props(obj);
+
+    if (vd->migration_blocked) {
+        error_setg(&vd->migration_blocker,
+                   "The vdagent chardev doesn't support migration with machine"
+                   " version less than 10.1");
+    }
+}
+
 static void vdagent_chr_fini(Object *obj)
 {
     VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
 
+    if (vd->migration_blocked) {
+        migrate_del_blocker(&vd->migration_blocker);
+    }
     vdagent_disconnect(vd);
     if (vd->mouse_hs) {
         qemu_input_handler_unregister(vd->mouse_hs);
@@ -1080,6 +1125,7 @@ static const TypeInfo vdagent_chr_type_info = {
     .parent = TYPE_CHARDEV,
     .instance_size = sizeof(VDAgentChardev),
     .instance_init = vdagent_chr_instance_init,
+    .instance_post_init = vdagent_post_init,
     .instance_finalize = vdagent_chr_fini,
     .class_init = vdagent_chr_class_init,
 };
-- 
2.47.3
Re: [PATCH v2] ui/vdagent: add migration blocker when machine version < 10.1
Posted by Fabiano Rosas 1 month ago 
Fiona Ebner <f.ebner@proxmox.com> writes:

> In QEMU 10.1, commit 5d56bff11e ("ui/vdagent: add migration support")
> added migration support for the vdagent chardev and commit 42000e0013
> ("ui/vdagent: remove migration blocker") removed the migration
> blocker. No compat for older machine versions was added, so migration
> with pre-10.1 machine version, from a 10.1 binary to a pre-10.1 binary
> will result in a failure when loading the VM state in the target
> instance:
>
>> Unknown savevm section or instance 'vdagent' 0. Make sure that your
>> current VM setup matches your saved VM setup, including any
>> hotplugged devices
>
> Add a compat flag to block migration when the machine version is less
> than 10.1 to avoid this.
>
> Cc: qemu-stable@nongnu.org
> Fixes: 42000e0013 ("ui/vdagent: remove migration blocker")
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Re: [PATCH v2] ui/vdagent: add migration blocker when machine version < 10.1
Posted by Marc-André Lureau 1 month ago 
Hi

On Tue, Mar 10, 2026 at 6:27 PM Fiona Ebner <f.ebner@proxmox.com> wrote:
>
> In QEMU 10.1, commit 5d56bff11e ("ui/vdagent: add migration support")
> added migration support for the vdagent chardev and commit 42000e0013
> ("ui/vdagent: remove migration blocker") removed the migration
> blocker. No compat for older machine versions was added, so migration
> with pre-10.1 machine version, from a 10.1 binary to a pre-10.1 binary
> will result in a failure when loading the VM state in the target
> instance:
>
> > Unknown savevm section or instance 'vdagent' 0. Make sure that your
> > current VM setup matches your saved VM setup, including any
> > hotplugged devices
>
> Add a compat flag to block migration when the machine version is less
> than 10.1 to avoid this.
>
> Cc: qemu-stable@nongnu.org
> Fixes: 42000e0013 ("ui/vdagent: remove migration blocker")
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

Ah yes, I didn't think about that case!
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
>
> Changes in v2:
> * rebase on current master, adapting to commit 8c84f31ace
>   ("chardev: .chr_open(): add boolean return value")
>
>  hw/core/machine.c |  1 +
>  ui/vdagent.c      | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a14ad05b9a..6cf0e2f404 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -57,6 +57,7 @@ GlobalProperty hw_compat_10_0[] = {
>      { "vfio-pci", "x-migration-load-config-after-iter", "off" },
>      { "ramfb", "use-legacy-x86-rom", "true"},
>      { "vfio-pci-nohotplug", "use-legacy-x86-rom", "true" },
> +    { "chardev-qemu-vdagent", "x-migration-blocked", "true" },
>  };
>  const size_t hw_compat_10_0_len = G_N_ELEMENTS(hw_compat_10_0);
>
> diff --git a/ui/vdagent.c b/ui/vdagent.c
> index 5a5e4bf681..bb0c4aa14c 100644
> --- a/ui/vdagent.c
> +++ b/ui/vdagent.c
> @@ -6,6 +6,8 @@
>  #include "qemu/option.h"
>  #include "qemu/units.h"
>  #include "hw/core/qdev.h"
> +#include "hw/core/qdev-properties.h"
> +#include "migration/blocker.h"
>  #include "ui/clipboard.h"
>  #include "ui/console.h"
>  #include "ui/input.h"
> @@ -24,6 +26,10 @@
>  struct VDAgentChardev {
>      Chardev parent;
>
> +    /* needed for machine versions < 10.1 when migration was not supported */
> +    Error *migration_blocker;
> +    bool migration_blocked;
> +
>      /* config */
>      bool mouse;
>      bool clipboard;
> @@ -657,6 +663,12 @@ static bool vdagent_chr_open(Chardev *chr, ChardevBackend *backend,
>      return false;
>  #endif
>
> +    if (vd->migration_blocked) {
> +        if (migrate_add_blocker(&vd->migration_blocker, errp) != 0) {
> +            return false;
> +        }
> +    }
> +
>      vd->mouse = VDAGENT_MOUSE_DEFAULT;
>      if (cfg->has_mouse) {
>          vd->mouse = cfg->mouse;
> @@ -901,6 +913,19 @@ static void vdagent_chr_parse(QemuOpts *opts, ChardevBackend *backend,
>
>  /* ------------------------------------------------------------------ */
>
> +static bool get_migration_blocked(Object *o, Error **errp)
> +{
> +    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(o);
> +    return vd->migration_blocked;
> +}
> +
> +static void set_migration_blocked(Object *o, bool migration_blocked,
> +                                   Error **errp)
> +{
> +    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(o);
> +    vd->migration_blocked = migration_blocked;
> +}
> +
>  static void vdagent_chr_class_init(ObjectClass *oc, const void *data)
>  {
>      ChardevClass *cc = CHARDEV_CLASS(oc);
> @@ -910,6 +935,10 @@ static void vdagent_chr_class_init(ObjectClass *oc, const void *data)
>      cc->chr_write        = vdagent_chr_write;
>      cc->chr_set_fe_open  = vdagent_chr_set_fe_open;
>      cc->chr_accept_input = vdagent_chr_accept_input;
> +
> +    object_class_property_add_bool(oc, "x-migration-blocked",
> +                                   get_migration_blocked,
> +                                   set_migration_blocked);
>  }
>
>  static int post_load(void *opaque, int version_id)
> @@ -1064,10 +1093,26 @@ static void vdagent_chr_instance_init(Object *obj)
>      vmstate_register_any(NULL, &vmstate_vdagent, vd);
>  }
>
> +static void vdagent_post_init(Object *obj)
> +{
> +    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
> +
> +    object_apply_compat_props(obj);
> +
> +    if (vd->migration_blocked) {
> +        error_setg(&vd->migration_blocker,
> +                   "The vdagent chardev doesn't support migration with machine"
> +                   " version less than 10.1");
> +    }
> +}
> +
>  static void vdagent_chr_fini(Object *obj)
>  {
>      VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
>
> +    if (vd->migration_blocked) {
> +        migrate_del_blocker(&vd->migration_blocker);
> +    }
>      vdagent_disconnect(vd);
>      if (vd->mouse_hs) {
>          qemu_input_handler_unregister(vd->mouse_hs);
> @@ -1080,6 +1125,7 @@ static const TypeInfo vdagent_chr_type_info = {
>      .parent = TYPE_CHARDEV,
>      .instance_size = sizeof(VDAgentChardev),
>      .instance_init = vdagent_chr_instance_init,
> +    .instance_post_init = vdagent_post_init,
>      .instance_finalize = vdagent_chr_fini,
>      .class_init = vdagent_chr_class_init,
>  };
> --
> 2.47.3
>
>
>


-- 
Marc-André Lureau

Patchew 2.1-devel-ea86937

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