Re: [xen_fbfront] - Xen PVH VM: kernel upgrade 6.9.10 > 6.10.7 results in crash

[Arthur Borsboom <arthurborsboom@xxxxxxxxx>]

On Sat, 7 Sept 2024 at 15:48, Jason Andryuk <jandryuk@xxxxxxxxx> wrote:
>
> From: Jason Andryuk <jason.andryuk@xxxxxxx>
>
> Hi Arthur,
>
> Can you give the patch below a try?  If it works, please respond with a
> Tested-by.  I'll then submit it with your Reported-by and Tested-by.

I have tested the following.

- Built and installed the Arch Linux AUR package linux-mainline:
6.11.0-rc6-1-mainline.
- Booted in PVH > failure: VM is inaccessible.
- Booted in HVM > success: VM is accessible.
- Applied the patch to the build above.
- Booted in PVH > success: VM is accessible.

>From my point of view this patch works and resolves the issue.
Hereby:

Tested-by: Arthur Borsboom <arthurborsboom@xxxxxxxxx>

Do you have an estimation in which kernel version this will land?

> Thanks,
> Jason
>
> [PATCH] fbdev/xen-fbfront: Assign fb_info->device
>
> Probing xen-fbfront faults in video_is_primary_device().  The passed-in
> struct device is NULL since xen-fbfront doesn't assign it and the
> memory is kzalloc()-ed.  Assign fb_info->device to avoid this.
>
> This was exposed by the conversion of fb_is_primary_device() to
> video_is_primary_device() which dropped a NULL check for struct device.
>
> Fixes: f178e96de7f0 ("arch: Remove struct fb_info from video helpers")
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
> ---
> The other option would be to re-instate the NULL check in
> video_is_primary_device()
> ---
>  drivers/video/fbdev/xen-fbfront.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/video/fbdev/xen-fbfront.c 
> b/drivers/video/fbdev/xen-fbfront.c
> index 66d4628a96ae..c90f48ebb15e 100644
> --- a/drivers/video/fbdev/xen-fbfront.c
> +++ b/drivers/video/fbdev/xen-fbfront.c
> @@ -407,6 +407,7 @@ static int xenfb_probe(struct xenbus_device *dev,
>         /* complete the abuse: */
>         fb_info->pseudo_palette = fb_info->par;
>         fb_info->par = info;
> +       fb_info->device = &dev->dev;
>
>         fb_info->screen_buffer = info->fb;
>
> --
> 2.43.0
>