Re: [PATCH] qxl: fix null-pointer crash during suspend

[Daniel Vetter]

On Tue, Sep 04, 2018 at 10:27:47PM +0200, Peter Wu wrote:
> "crtc->helper_private" is not initialized by the QXL driver and thus the

This is still initialized, it's the ->disable that goes boom. At least the
call to drm_crtc_helper_add is still there. The ->disable was removed in:

commit 64581714b58bc3e16ede8dc37a025c3aa0e0eef1
Author: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
Date:   Fri Jun 30 12:36:45 2017 +0300

    drm: Convert atomic drivers from CRTC .disable() to .atomic_disable()

Fixes: 64581714b58b ("drm: Convert atomic drivers from CRTC .disable() to .atomic_disable()")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

I'll let Gerd pick this one up, after some testing. Also adding Laurent.
-Daniel

> "crtc_funcs->disable" call would crash (resulting in suspend failure).
> Fix this by converting the suspend/resume functions to use the
> drm_mode_config_helper_* helpers.
> 
> Tested system sleep with QEMU 3.0 using "echo mem > /sys/power/state".
> During suspend the following message is visible from QEMU:
> 
>     spice/server/display-channel.c:2425:display_channel_validate_surface: canvas address is 0x7fd05da68308 for 0 (and is NULL)
>     spice/server/display-channel.c:2426:display_channel_validate_surface: failed on 0
> 
> This seems to be triggered by QXL_IO_NOTIFY_CMD after
> QXL_IO_DESTROY_PRIMARY_ASYNC, but aside from the warning things still
> seem to work (tested with both the GTK and -spice options).
> 
> Signed-off-by: Peter Wu <peter@xxxxxxxxxxxxx>
> ---
> Hi,
> 
> I found this issue while trying to suspend a VM that uses QXL. In order to see
> the stack trace over serial, boot with no_console_suspend. Searching for
> "qxl_drm_freeze" showed one recent report from Alan:
> https://lkml.kernel.org/r/891e334c-cf19-032c-b996-59ac166fcde1@xxxxxxxxx
> 
> Kind regards,
> Peter
> ---
>  drivers/gpu/drm/qxl/qxl_drv.c | 26 +++++---------------------
>  1 file changed, 5 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c
> index 2445e75cf7ea..d00f45eed03c 100644
> --- a/drivers/gpu/drm/qxl/qxl_drv.c
> +++ b/drivers/gpu/drm/qxl/qxl_drv.c
> @@ -136,20 +136,11 @@ static int qxl_drm_freeze(struct drm_device *dev)
>  {
>  	struct pci_dev *pdev = dev->pdev;
>  	struct qxl_device *qdev = dev->dev_private;
> -	struct drm_crtc *crtc;
> -
> -	drm_kms_helper_poll_disable(dev);
> -
> -	console_lock();
> -	qxl_fbdev_set_suspend(qdev, 1);
> -	console_unlock();
> +	int ret;
>  
> -	/* unpin the front buffers */
> -	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> -		const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
> -		if (crtc->enabled)
> -			(*crtc_funcs->disable)(crtc);
> -	}
> +	ret = drm_mode_config_helper_suspend(dev);
> +	if (ret)
> +		return ret;
>  
>  	qxl_destroy_monitors_object(qdev);
>  	qxl_surf_evict(qdev);
> @@ -175,14 +166,7 @@ static int qxl_drm_resume(struct drm_device *dev, bool thaw)
>  	}
>  
>  	qxl_create_monitors_object(qdev);
> -	drm_helper_resume_force_mode(dev);
> -
> -	console_lock();
> -	qxl_fbdev_set_suspend(qdev, 0);
> -	console_unlock();
> -
> -	drm_kms_helper_poll_enable(dev);
> -	return 0;
> +	return drm_mode_config_helper_resume(dev);
>  }
>  
>  static int qxl_pm_suspend(struct device *dev)
> -- 
> 2.18.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch