RE: [PATCH v2] video: hyperv: hyperv_fb: refresh the VM screen by force on VM panic

[Dexuan Cui]

> -----Original Message-----
> From: driverdev-devel-bounces@xxxxxxxxxxxxxxxxxxxxxx [mailto:driverdev-
> devel-bounces@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Dexuan Cui
> Sent: Friday, June 27, 2014 5:35 AM
> To: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; driverdev-
> devel@xxxxxxxxxxxxxxxxxxxxxx; plagnioj@xxxxxxxxxxxx;
> tomi.valkeinen@xxxxxx; linux-fbdev@xxxxxxxxxxxxxxx; olaf@xxxxxxxxx;
> apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx
> Cc: Haiyang Zhang
> Subject: [PATCH v2] video: hyperv: hyperv_fb: refresh the VM screen by force
> on VM panic
> 
> Currently the VSC has no chance to notify the VSP of the dirty rectangle on
> VM
> panic because the notification work is done in a workqueue, and in panic()
> the
> kernel typically ends up in an infinite loop, and a typical kernel config has
> CONFIG_PREEMPT_VOLUNTARY=y and CONFIG_PREEMPT is not set, so a
> context switch
> can't happen in panic() and the workqueue won't have a chance to run. As a
> result, the VM Connection window can't refresh until it's closed and we
> re-connect to the VM.
> 
> We can register a handler on panic_notifier_list: the handler can notify
> the VSC and switch the framebuffer driver to a "synchronous mode",
> meaning
> the VSC flushes any future framebuffer change to the VSP immediately.
> 
> v2: removed the MS-TFS line in the commit message
> 
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

Hi Greg, Tomi, Jean and all,
Any new comment for the patch?

Thanks,
-- Dexuan

> ---
>  drivers/video/fbdev/hyperv_fb.c | 58
> ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 55 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/fbdev/hyperv_fb.c
> b/drivers/video/fbdev/hyperv_fb.c
> index e23392e..291d171 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -226,11 +226,16 @@ struct hvfb_par {
>  	u8 recv_buf[MAX_VMBUS_PKT_SIZE];
>  };
> 
> +static struct fb_info *hvfb_info;
> +
>  static uint screen_width = HVFB_WIDTH;
>  static uint screen_height = HVFB_HEIGHT;
>  static uint screen_depth;
>  static uint screen_fb_size;
> 
> +/* If true, the VSC notifies the VSP on every framebuffer change */
> +static bool synchronous_fb;
> +
>  /* Send message to Hyper-V host */
>  static inline int synthvid_send(struct hv_device *hdev,
>  				struct synthvid_msg *msg)
> @@ -532,6 +537,20 @@ static void hvfb_update_work(struct work_struct *w)
>  		schedule_delayed_work(&par->dwork,
> HVFB_UPDATE_DELAY);
>  }
> 
> +static int hvfb_on_panic(struct notifier_block *nb,
> +			unsigned long e, void *p)
> +{
> +	if (hvfb_info)
> +		synthvid_update(hvfb_info);
> +
> +	synchronous_fb = true;
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block hvfb_panic_nb = {
> +	.notifier_call = hvfb_on_panic,
> +};
> 
>  /* Framebuffer operation handlers */
> 
> @@ -582,14 +601,41 @@ static int hvfb_blank(int blank, struct fb_info *info)
>  	return 1;	/* get fb_blank to set the colormap to all black */
>  }
> 
> +static void hvfb_cfb_fillrect(struct fb_info *p,
> +				const struct fb_fillrect *rect)
> +{
> +	cfb_fillrect(p, rect);
> +
> +	if (unlikely(synchronous_fb))
> +		synthvid_update(p);
> +}
> +
> +static void hvfb_cfb_copyarea(struct fb_info *p,
> +				const struct fb_copyarea *area)
> +{
> +	cfb_copyarea(p, area);
> +
> +	if (unlikely(synchronous_fb))
> +		synthvid_update(p);
> +}
> +
> +static void hvfb_cfb_imageblit(struct fb_info *p,
> +				const struct fb_image *image)
> +{
> +	cfb_imageblit(p, image);
> +
> +	if (unlikely(synchronous_fb))
> +		synthvid_update(p);
> +}
> +
>  static struct fb_ops hvfb_ops = {
>  	.owner = THIS_MODULE,
>  	.fb_check_var = hvfb_check_var,
>  	.fb_set_par = hvfb_set_par,
>  	.fb_setcolreg = hvfb_setcolreg,
> -	.fb_fillrect = cfb_fillrect,
> -	.fb_copyarea = cfb_copyarea,
> -	.fb_imageblit = cfb_imageblit,
> +	.fb_fillrect = hvfb_cfb_fillrect,
> +	.fb_copyarea = hvfb_cfb_copyarea,
> +	.fb_imageblit = hvfb_cfb_imageblit,
>  	.fb_blank = hvfb_blank,
>  };
> 
> @@ -801,6 +847,9 @@ static int hvfb_probe(struct hv_device *hdev,
> 
>  	par->fb_ready = true;
> 
> +	hvfb_info = info;
> +	atomic_notifier_chain_register(&panic_notifier_list,
> &hvfb_panic_nb);
> +
>  	return 0;
> 
>  error:
> @@ -820,6 +869,9 @@ static int hvfb_remove(struct hv_device *hdev)
>  	struct fb_info *info = hv_get_drvdata(hdev);
>  	struct hvfb_par *par = info->par;
> 
> +	atomic_notifier_chain_unregister(&panic_notifier_list,
> &hvfb_panic_nb);
> +	hvfb_info = NULL;
> +
>  	par->update = false;
>  	par->fb_ready = false;
> 
> --
> 1.9.1
> 
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