From: Alessandro Ratti <alessandro@0x65c.net>

Replace virtio_error() with a macro that automatically prepends the
calling function name to error messages. This provides better context
for debugging virtio issues by showing exactly which function
encountered the error.

Before: "Invalid queue size: 1024"
After:  "virtio_queue_set_num: Invalid queue size: 1024"

The implementation uses a macro to insert __func__ at compile time,
avoiding any runtime overhead while providing more specific error
context than a generic "virtio:" prefix.

Also remove manual __func__ usage in virtio-balloon to avoid duplicate
function names in error messages.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250915162643.44716-2-alessandro@0x65c.net>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h | 4 +++-
 hw/virtio/virtio-balloon.c | 2 +-
 hw/virtio/virtio.c         | 3 ++-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index d97529c3f1..695bb56186 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -253,7 +253,9 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size);
 
 void virtio_cleanup(VirtIODevice *vdev);
 
-void virtio_error(VirtIODevice *vdev, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
+#define virtio_error(vdev, fmt, ...) \
+    virtio_error_impl(vdev, "%s: " fmt, __func__, ##__VA_ARGS__)
+void virtio_error_impl(VirtIODevice *, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
 
 /* Set the child bus name. */
 void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index db787d00b3..e443f71c01 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -697,7 +697,7 @@ virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data,
     case PRECOPY_NOTIFY_COMPLETE:
         break;
     default:
-        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
+        virtio_error(vdev, "%d reason unknown", pnd->reason);
     }
 
     return 0;
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index de89e8104a..0f33ca5d90 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3968,7 +3968,8 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
     vdev->bus_name = g_strdup(bus_name);
 }
 
-void G_GNUC_PRINTF(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
+void G_GNUC_PRINTF(2, 3)
+virtio_error_impl(VirtIODevice *vdev, const char *fmt, ...)
 {
     va_list ap;
 
-- 
MST

On Sun, 5 Oct 2025 at 21:17, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Alessandro Ratti <alessandro@0x65c.net>
>
> Replace virtio_error() with a macro that automatically prepends the
> calling function name to error messages. This provides better context
> for debugging virtio issues by showing exactly which function
> encountered the error.
>
> Before: "Invalid queue size: 1024"
> After:  "virtio_queue_set_num: Invalid queue size: 1024"
>
> The implementation uses a macro to insert __func__ at compile time,
> avoiding any runtime overhead while providing more specific error
> context than a generic "virtio:" prefix.
>
> Also remove manual __func__ usage in virtio-balloon to avoid duplicate
> function names in error messages.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
> Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Message-ID: <20250915162643.44716-2-alessandro@0x65c.net>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  include/hw/virtio/virtio.h | 4 +++-
>  hw/virtio/virtio-balloon.c | 2 +-
>  hw/virtio/virtio.c         | 3 ++-
>  3 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index d97529c3f1..695bb56186 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -253,7 +253,9 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size);
>
>  void virtio_cleanup(VirtIODevice *vdev);
>
> -void virtio_error(VirtIODevice *vdev, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> +#define virtio_error(vdev, fmt, ...) \
> +    virtio_error_impl(vdev, "%s: " fmt, __func__, ##__VA_ARGS__)
> +void virtio_error_impl(VirtIODevice *, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
>
>  /* Set the child bus name. */
>  void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index db787d00b3..e443f71c01 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -697,7 +697,7 @@ virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data,
>      case PRECOPY_NOTIFY_COMPLETE:
>          break;
>      default:
> -        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
> +        virtio_error(vdev, "%d reason unknown", pnd->reason);
>      }
>
>      return 0;
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index de89e8104a..0f33ca5d90 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -3968,7 +3968,8 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
>      vdev->bus_name = g_strdup(bus_name);
>  }
>
> -void G_GNUC_PRINTF(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
> +void G_GNUC_PRINTF(2, 3)
> +virtio_error_impl(VirtIODevice *vdev, const char *fmt, ...)
>  {
>      va_list ap;
>
> --
> MST
>
>

Hi Michael,

Thanks for picking this up.

It seems that the version currently queued is actually the initial
submission, which had previously been rejected following feedback from
Markus Armbruster.
I later submitted a corrected version ([v3]) which:

* Addresses all the feedback (including from Markus Armbruster and
Daniel P. Berrangé).
* Has Daniel’s formal Reviewed-by:

Patch: https://lore.kernel.org/qemu-devel/20250924093138.559872-2-alessandro@0x65c.net/
Reviewed-by: https://lore.kernel.org/qemu-devel/aNO7J7Y6wsk1-wyw@redhat.com/

Would you mind updating the queue to reflect this version instead?

Thanks again for your time and all the work you do maintaining virtio!

Best regards,
Alessandro

On Sun, Oct 05, 2025 at 10:13:57PM +0200, Alessandro Ratti wrote:
> On Sun, 5 Oct 2025 at 21:17, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > From: Alessandro Ratti <alessandro@0x65c.net>
> >
> > Replace virtio_error() with a macro that automatically prepends the
> > calling function name to error messages. This provides better context
> > for debugging virtio issues by showing exactly which function
> > encountered the error.
> >
> > Before: "Invalid queue size: 1024"
> > After:  "virtio_queue_set_num: Invalid queue size: 1024"
> >
> > The implementation uses a macro to insert __func__ at compile time,
> > avoiding any runtime overhead while providing more specific error
> > context than a generic "virtio:" prefix.
> >
> > Also remove manual __func__ usage in virtio-balloon to avoid duplicate
> > function names in error messages.
> >
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
> > Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
> > Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> > Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > Message-ID: <20250915162643.44716-2-alessandro@0x65c.net>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/hw/virtio/virtio.h | 4 +++-
> >  hw/virtio/virtio-balloon.c | 2 +-
> >  hw/virtio/virtio.c         | 3 ++-
> >  3 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index d97529c3f1..695bb56186 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -253,7 +253,9 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size);
> >
> >  void virtio_cleanup(VirtIODevice *vdev);
> >
> > -void virtio_error(VirtIODevice *vdev, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> > +#define virtio_error(vdev, fmt, ...) \
> > +    virtio_error_impl(vdev, "%s: " fmt, __func__, ##__VA_ARGS__)
> > +void virtio_error_impl(VirtIODevice *, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> >
> >  /* Set the child bus name. */
> >  void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
> > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> > index db787d00b3..e443f71c01 100644
> > --- a/hw/virtio/virtio-balloon.c
> > +++ b/hw/virtio/virtio-balloon.c
> > @@ -697,7 +697,7 @@ virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data,
> >      case PRECOPY_NOTIFY_COMPLETE:
> >          break;
> >      default:
> > -        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
> > +        virtio_error(vdev, "%d reason unknown", pnd->reason);
> >      }
> >
> >      return 0;
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index de89e8104a..0f33ca5d90 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -3968,7 +3968,8 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
> >      vdev->bus_name = g_strdup(bus_name);
> >  }
> >
> > -void G_GNUC_PRINTF(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
> > +void G_GNUC_PRINTF(2, 3)
> > +virtio_error_impl(VirtIODevice *vdev, const char *fmt, ...)
> >  {
> >      va_list ap;
> >
> > --
> > MST
> >
> >
> 
> Hi Michael,
> 
> Thanks for picking this up.
> 
> It seems that the version currently queued is actually the initial
> submission, which had previously been rejected following feedback from
> Markus Armbruster.
> I later submitted a corrected version ([v3]) which:
> 
> * Addresses all the feedback (including from Markus Armbruster and
> Daniel P. Berrangé).
> * Has Daniel’s formal Reviewed-by:
> 
> Patch: https://lore.kernel.org/qemu-devel/20250924093138.559872-2-alessandro@0x65c.net/
> Reviewed-by: https://lore.kernel.org/qemu-devel/aNO7J7Y6wsk1-wyw@redhat.com/
> 
> Would you mind updating the queue to reflect this version instead?
> 
> Thanks again for your time and all the work you do maintaining virtio!
> 
> Best regards,
> Alessandro


So as you likely already noticed
I replaced just this patch and updated the tag in the pull.

-- 
MST

On Wed, 8 Oct 2025 at 12:01, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Sun, Oct 05, 2025 at 10:13:57PM +0200, Alessandro Ratti wrote:
> > On Sun, 5 Oct 2025 at 21:17, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >
> > > From: Alessandro Ratti <alessandro@0x65c.net>
> > >
> > > Replace virtio_error() with a macro that automatically prepends the
> > > calling function name to error messages. This provides better context
> > > for debugging virtio issues by showing exactly which function
> > > encountered the error.
> > >
> > > Before: "Invalid queue size: 1024"
> > > After:  "virtio_queue_set_num: Invalid queue size: 1024"
> > >
> > > The implementation uses a macro to insert __func__ at compile time,
> > > avoiding any runtime overhead while providing more specific error
> > > context than a generic "virtio:" prefix.
> > >
> > > Also remove manual __func__ usage in virtio-balloon to avoid duplicate
> > > function names in error messages.
> > >
> > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
> > > Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
> > > Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> > > Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
> > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > > Message-ID: <20250915162643.44716-2-alessandro@0x65c.net>
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > >  include/hw/virtio/virtio.h | 4 +++-
> > >  hw/virtio/virtio-balloon.c | 2 +-
> > >  hw/virtio/virtio.c         | 3 ++-
> > >  3 files changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > > index d97529c3f1..695bb56186 100644
> > > --- a/include/hw/virtio/virtio.h
> > > +++ b/include/hw/virtio/virtio.h
> > > @@ -253,7 +253,9 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size);
> > >
> > >  void virtio_cleanup(VirtIODevice *vdev);
> > >
> > > -void virtio_error(VirtIODevice *vdev, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> > > +#define virtio_error(vdev, fmt, ...) \
> > > +    virtio_error_impl(vdev, "%s: " fmt, __func__, ##__VA_ARGS__)
> > > +void virtio_error_impl(VirtIODevice *, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> > >
> > >  /* Set the child bus name. */
> > >  void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
> > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> > > index db787d00b3..e443f71c01 100644
> > > --- a/hw/virtio/virtio-balloon.c
> > > +++ b/hw/virtio/virtio-balloon.c
> > > @@ -697,7 +697,7 @@ virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data,
> > >      case PRECOPY_NOTIFY_COMPLETE:
> > >          break;
> > >      default:
> > > -        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
> > > +        virtio_error(vdev, "%d reason unknown", pnd->reason);
> > >      }
> > >
> > >      return 0;
> > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > index de89e8104a..0f33ca5d90 100644
> > > --- a/hw/virtio/virtio.c
> > > +++ b/hw/virtio/virtio.c
> > > @@ -3968,7 +3968,8 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
> > >      vdev->bus_name = g_strdup(bus_name);
> > >  }
> > >
> > > -void G_GNUC_PRINTF(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
> > > +void G_GNUC_PRINTF(2, 3)
> > > +virtio_error_impl(VirtIODevice *vdev, const char *fmt, ...)
> > >  {
> > >      va_list ap;
> > >
> > > --
> > > MST
> > >
> > >
> >
> > Hi Michael,
> >
> > Thanks for picking this up.
> >
> > It seems that the version currently queued is actually the initial
> > submission, which had previously been rejected following feedback from
> > Markus Armbruster.
> > I later submitted a corrected version ([v3]) which:
> >
> > * Addresses all the feedback (including from Markus Armbruster and
> > Daniel P. Berrangé).
> > * Has Daniel’s formal Reviewed-by:
> >
> > Patch: https://lore.kernel.org/qemu-devel/20250924093138.559872-2-alessandro@0x65c.net/
> > Reviewed-by: https://lore.kernel.org/qemu-devel/aNO7J7Y6wsk1-wyw@redhat.com/
> >
> > Would you mind updating the queue to reflect this version instead?
> >
> > Thanks again for your time and all the work you do maintaining virtio!
> >
> > Best regards,
> > Alessandro
>
>
> So as you likely already noticed
> I replaced just this patch and updated the tag in the pull.

Thanks Michael, I saw the update — everything looks good on my end.
I really appreciate you taking the time to sort that out!

Best regards,
Alessandro

On Sun, Oct 05, 2025 at 10:13:57PM +0200, Alessandro Ratti wrote:
> On Sun, 5 Oct 2025 at 21:17, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > From: Alessandro Ratti <alessandro@0x65c.net>
> >
> > Replace virtio_error() with a macro that automatically prepends the
> > calling function name to error messages. This provides better context
> > for debugging virtio issues by showing exactly which function
> > encountered the error.
> >
> > Before: "Invalid queue size: 1024"
> > After:  "virtio_queue_set_num: Invalid queue size: 1024"
> >
> > The implementation uses a macro to insert __func__ at compile time,
> > avoiding any runtime overhead while providing more specific error
> > context than a generic "virtio:" prefix.
> >
> > Also remove manual __func__ usage in virtio-balloon to avoid duplicate
> > function names in error messages.
> >
> > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
> > Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
> > Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> > Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > Message-ID: <20250915162643.44716-2-alessandro@0x65c.net>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/hw/virtio/virtio.h | 4 +++-
> >  hw/virtio/virtio-balloon.c | 2 +-
> >  hw/virtio/virtio.c         | 3 ++-
> >  3 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index d97529c3f1..695bb56186 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -253,7 +253,9 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size);
> >
> >  void virtio_cleanup(VirtIODevice *vdev);
> >
> > -void virtio_error(VirtIODevice *vdev, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> > +#define virtio_error(vdev, fmt, ...) \
> > +    virtio_error_impl(vdev, "%s: " fmt, __func__, ##__VA_ARGS__)
> > +void virtio_error_impl(VirtIODevice *, const char *fmt, ...) G_GNUC_PRINTF(2, 3);
> >
> >  /* Set the child bus name. */
> >  void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
> > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> > index db787d00b3..e443f71c01 100644
> > --- a/hw/virtio/virtio-balloon.c
> > +++ b/hw/virtio/virtio-balloon.c
> > @@ -697,7 +697,7 @@ virtio_balloon_free_page_hint_notify(NotifierWithReturn *n, void *data,
> >      case PRECOPY_NOTIFY_COMPLETE:
> >          break;
> >      default:
> > -        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
> > +        virtio_error(vdev, "%d reason unknown", pnd->reason);
> >      }
> >
> >      return 0;
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index de89e8104a..0f33ca5d90 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -3968,7 +3968,8 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
> >      vdev->bus_name = g_strdup(bus_name);
> >  }
> >
> > -void G_GNUC_PRINTF(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
> > +void G_GNUC_PRINTF(2, 3)
> > +virtio_error_impl(VirtIODevice *vdev, const char *fmt, ...)
> >  {
> >      va_list ap;
> >
> > --
> > MST
> >
> >
> 
> Hi Michael,
> 
> Thanks for picking this up.
> 
> It seems that the version currently queued is actually the initial
> submission, which had previously been rejected following feedback from
> Markus Armbruster.
> I later submitted a corrected version ([v3]) which:
> 
> * Addresses all the feedback (including from Markus Armbruster and
> Daniel P. Berrangé).
> * Has Daniel’s formal Reviewed-by:
> 
> Patch: https://lore.kernel.org/qemu-devel/20250924093138.559872-2-alessandro@0x65c.net/
> Reviewed-by: https://lore.kernel.org/qemu-devel/aNO7J7Y6wsk1-wyw@redhat.com/
> 
> Would you mind updating the queue to reflect this version instead?
> 
> Thanks again for your time and all the work you do maintaining virtio!
> 
> Best regards,
> Alessandro


Oh right. The weird thing is that I reviewed v3 but because it was
a reply when i applied it using b4 it actually picked up original one.
Not good! pls start a new thread each time.

From: Alessandro Ratti <alessandro@0x65c.net>

Improve error reporting when virtqueue ring mapping fails by including a
device identifier in the error message.

Introduce a helper qdev_get_printable_name() in qdev-core, which returns
either:

 - the device ID, if explicitly provided (e.g. -device ...,id=foo)
 - the QOM path from qdev_get_dev_path(dev) otherwise
 - "<unknown device>" as a fallback when no identifier is present

This makes it easier to identify which device triggered the error in
multi-device setups or when debugging complex guest configurations.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/230
Buglink: https://bugs.launchpad.net/qemu/+bug/1919021
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Alessandro Ratti <alessandro@0x65c.net>
Message-Id: <20250924093138.559872-2-alessandro@0x65c.net>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/qdev-core.h |  1 +
 hw/core/qdev.c         | 29 +++++++++++++++++++++++++++++
 hw/virtio/virtio.c     | 15 ++++++++++++---
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 530f3da702..a7bfb10dc7 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -1064,6 +1064,7 @@ bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error **errp);
 extern bool qdev_hot_removed;
 
 char *qdev_get_dev_path(DeviceState *dev);
+const char *qdev_get_printable_name(DeviceState *dev);
 
 void qbus_set_hotplug_handler(BusState *bus, Object *handler);
 void qbus_set_bus_hotplug_handler(BusState *bus);
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index f600226176..fab42a7270 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -411,6 +411,35 @@ char *qdev_get_dev_path(DeviceState *dev)
     return NULL;
 }
 
+const char *qdev_get_printable_name(DeviceState *vdev)
+{
+    /*
+     * Return device ID if explicity set
+     * (e.g. -device virtio-blk-pci,id=foo)
+     * This allows users to correlate errors with their custom device
+     * names.
+     */
+    if (vdev->id) {
+        return vdev->id;
+    }
+    /*
+     * Fall back to the canonical QOM device path (eg. ID for PCI
+     * devices).
+     * This ensures the device is still uniquely and meaningfully
+     * identified.
+     */
+    const char *path = qdev_get_dev_path(vdev);
+    if (path) {
+        return path;
+    }
+
+    /*
+     * Final fallback: if all else fails, return a placeholder string.
+     * This ensures the error message always contains a valid string.
+     */
+    return "<unknown device>";
+}
+
 void qdev_add_unplug_blocker(DeviceState *dev, Error *reason)
 {
     dev->unplug_blockers = g_slist_prepend(dev->unplug_blockers, reason);
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index de89e8104a..d38aafe5eb 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -257,7 +257,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->desc, vdev->dma_as,
                                    addr, size, packed);
     if (len < size) {
-        virtio_error(vdev, "Cannot map desc");
+        virtio_error(vdev,
+                "Failed to map descriptor ring for device %s: "
+                "invalid guest physical address or corrupted queue setup",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_desc;
     }
 
@@ -265,7 +268,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->used, vdev->dma_as,
                                    vq->vring.used, size, true);
     if (len < size) {
-        virtio_error(vdev, "Cannot map used");
+        virtio_error(vdev,
+                "Failed to map used ring for device %s: "
+                "possible guest misconfiguration or insufficient memory",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_used;
     }
 
@@ -273,7 +279,10 @@ void virtio_init_region_cache(VirtIODevice *vdev, int n)
     len = address_space_cache_init(&new->avail, vdev->dma_as,
                                    vq->vring.avail, size, false);
     if (len < size) {
-        virtio_error(vdev, "Cannot map avail");
+        virtio_error(vdev,
+                "Failed to map avalaible ring for device %s: "
+                "possible queue misconfiguration or overlapping memory region",
+                qdev_get_printable_name(DEVICE(vdev)));
         goto err_avail;
     }
 
-- 
MST