linux-kernel - Re: [PATCH v2] virtgpu: don't reset on shutdown

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Message-ID: <lgizdflxcku5ew2en55ux3r72u37d6aycuoosn5i5a5wagz6sc@d2kha7ycmmpy>
Date: Wed, 16 Apr 2025 15:57:11 +0200
From: Gerd Hoffmann <kraxel@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, Eric Auger <eric.auger@...hat.com>, 
	Eric Auger <eauger@...hat.com>, Jocelyn Falempe <jfalempe@...hat.com>, 
	David Airlie <airlied@...hat.com>, Gurchetan Singh <gurchetansingh@...omium.org>, 
	Chia-I Wu <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Simona Vetter <simona@...ll.ch>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez <eperezma@...hat.com>, 
	dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev
Subject: Re: [PATCH v2] virtgpu: don't reset on shutdown

On Tue, Apr 15, 2025 at 10:00:48AM -0400, Michael S. Tsirkin wrote:
> On Tue, Apr 15, 2025 at 01:16:32PM +0200, Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > +static void virtio_gpu_shutdown(struct virtio_device *vdev)
> > > +{
> > > +	/*
> > > +	 * drm does its own synchronization on shutdown.
> > > +	 * Do nothing here, opt out of device reset.
> > > +	 */
> > 
> > I think a call to 'drm_dev_unplug()' is what you need here.
> > 
> > take care,
> >   Gerd
> 
> My patch reverts the behaviour back to what it was, so pls go
> ahead and send a patch on top? I won't be able to explain
> what it does and why it's needed.

See below.  Untested.

Eric, can you give this a spin?

thanks,
  Gerd

----------------------- cut here -------------------------------
>From f3051dd52cb2004232941e6d2cbc0c694e290534 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@...hat.com>
Date: Wed, 16 Apr 2025 15:53:04 +0200
Subject: [PATCH] drm/virtio: implement virtio_gpu_shutdown

Calling drm_dev_unplug() is the drm way to say the device
is gone and can not be accessed any more.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
index e32e680c7197..71c6ccad4b99 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.c
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
@@ -130,10 +130,10 @@ static void virtio_gpu_remove(struct virtio_device *vdev)
 
 static void virtio_gpu_shutdown(struct virtio_device *vdev)
 {
-	/*
-	 * drm does its own synchronization on shutdown.
-	 * Do nothing here, opt out of device reset.
-	 */
+	struct drm_device *dev = vdev->priv;
+
+	/* stop talking to the device */
+	drm_dev_unplug(dev);
 }
 
 static void virtio_gpu_config_changed(struct virtio_device *vdev)
-- 
2.49.0