On 10/03/16 18:43, Emil Velikov wrote:
> Earlier commit was removing all the users of drm_platform_set_busid and
> removed the virtio hunk (which uses the PCI version of the function) by
> mistake.
>
> This in itself resulted in user space receiving an incorrect value for
> the busid, which in the case below lead to the failure to detect
> the (correct) device and ultimately the X server failing to start.
>
> Fixes: a325725633c ("drm: Lobotomize set_busid nonsense for !pci
> drivers")
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Laszlo Ersek <lersek@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1366842
> Reported-by: Laszlo Ersek <lersek@xxxxxxxxxx>
> Signed-off-by: Emil Velikov <emil.l.velikov@xxxxxxxxx>
> ---
> Since I'm not 100% sure if we can get into .set_busid() as pci_dev is
> NULL (for the virtio-vga 'vs' virgio-gpu-pci case) I've left the local
> wrapper.
>
> Note: patch is against mainline (refs/tags/v4.8) but should apply for
> drm-next/others.
> ---
> drivers/gpu/drm/virtio/virtgpu_drm_bus.c | 10 ++++++++++
> drivers/gpu/drm/virtio/virtgpu_drv.c | 1 +
> drivers/gpu/drm/virtio/virtgpu_drv.h | 1 +
> 3 files changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drm_bus.c b/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> index 7f0e93f87..88a3916 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drm_bus.c
> @@ -27,6 +27,16 @@
>
> #include "virtgpu_drv.h"
>
> +int drm_virtio_set_busid(struct drm_device *dev, struct drm_master *master)
> +{
> + struct pci_dev *pdev = dev->pdev;
> +
> + if (pdev) {
> + return drm_pci_set_busid(dev, master);
> + }
> + return 0;
> +}
> +
> static void virtio_pci_kick_out_firmware_fb(struct pci_dev *pci_dev)
> {
> struct apertures_struct *ap;
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index c13f70c..5820b702 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -117,6 +117,7 @@ static const struct file_operations virtio_gpu_driver_fops = {
>
> static struct drm_driver driver = {
> .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_PRIME | DRIVER_RENDER | DRIVER_ATOMIC,
> + .set_busid = drm_virtio_set_busid,
> .load = virtio_gpu_driver_load,
> .unload = virtio_gpu_driver_unload,
> .open = virtio_gpu_driver_open,
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
> index b18ef31..acf556a 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
> @@ -49,6 +49,7 @@
> #define DRIVER_PATCHLEVEL 1
>
> /* virtgpu_drm_bus.c */
> +int drm_virtio_set_busid(struct drm_device *dev, struct drm_master *master);
> int drm_virtio_init(struct drm_driver *driver, struct virtio_device *vdev);
>
> struct virtio_gpu_object {
>
I've come up with the identical patch (code-wise). I haven't posted it yet because:
- I'd like to reproduce the original issue with the fresh 4.8 kernel, using the F24 config (so the build is taking forever :( :( :(),
- I'd like to test the patch too.
Obviously, testing your patch is just as good as testing my (identical) patch, it's just that I'll have to respond with a Tested-by.
However, my commit message is different; what do you think of it?
--------
commit a005c99587ce52b60cfae897071f124cc5867347
Author: Laszlo Ersek <lersek@xxxxxxxxxx>
Date: Mon Oct 3 17:59:14 2016 +0200
drm: virtio: reinstate drm_virtio_set_busid()
Before commit a325725633c2 ("drm: Lobotomize set_busid nonsense for !pci
drivers"), several DRM drivers for platform devices used to expose an
explicit "drm_driver.set_busid" callback, invariably backed by
drm_platform_set_busid().
Commit a325725633c2 removed drm_platform_set_busid(), along with the
referring .set_busid field initializations. This was justified because
interchangeable functionality had been implemented in drm_dev_alloc() /
drm_dev_init(), which DRM_IOCTL_SET_VERSION would rely on going forward.
However, commit a325725633c2 also removed drm_virtio_set_busid(), for
which the same consolidation was not appropriate: this .set_busid callback
had been implemented with drm_pci_set_busid(), and not
drm_platform_set_busid(). The error regressed Xorg/xserver on QEMU's
"virtio-vga" card; the drmGetBusid() function from libdrm would no longer
return stable PCI identifiers like "pci:0000:00:02.0", but rather unstable
platform ones like "virtio0".
Reinstate drm_virtio_set_busid() with judicious use of
git checkout -p a325725633c2^ -- drivers/gpu/drm/virtio
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxxx>
Cc: Emil Velikov <emil.l.velikov@xxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: Joachim Frieben <jfrieben@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Joachim Frieben <jfrieben@xxxxxxxxxxx>
Fixes: a325725633c26aa66ab940f762a6b0778edf76c0
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1366842
Signed-off-by: Laszlo Ersek <lersek@xxxxxxxxxx>
drivers/gpu/drm/virtio/virtgpu_drm_bus.c | 10 ++++++++++
drivers/gpu/drm/virtio/virtgpu_drv.c | 1 +
drivers/gpu/drm/virtio/virtgpu_drv.h | 1 +
3 files changed, 12 insertions(+)
--------
I obviously don't "insist" that you take my commit message :), but you might want to scavenge it for some bits. You might not as well. :)
Regarding the local wrapper around drm_pci_set_busid(): that's not because of virtio-vga vs. virtio-gpu-pci. Instead, it's due to the virtio-mmio vs. virtio-pci transports that are possible for virtio devices. Theoretically at least, a virtio-gpu device could be exposed by QEMU as a memory mapped device in arm/arm64 guests. In that case the "platform bus ID" would simply be the base address of the virtio-mmio register block.
In practice, virtio-gpu over virtio-mmio would be an extremely outlandish configuration (noone does / should do that, plain and simple). Which is why implementing actual "platform bus ID" logic for the virtio-mmio transport case is unnecessary. It's just that the kernel shouldn't crash even if someone tries virtio-gpu over virtio-mmio.
So, the wrapper function (with the pdev nullity check) should be preserved, even if not entirely for the reason you suspected.
Anyway, my laptop seems to have ceased emitting sounds resembling a gas turbine, which I'll take as the completion of the 4.8 kernel build. Will be back soon with test results...
Thanks!
Laszlo
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