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

[Arthur Borsboom <arthurborsboom@xxxxxxxxx>]

Hi Jason,

JA> Can you give the patch below a try?  If it works, please respond with a 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?

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.

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