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 <[email protected]>
Reviewed-by: Haiyang Zhang <[email protected]>
---
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
> -----Original Message-----
> From: [email protected] [mailto:driverdev-
> [email protected]] On Behalf Of Dexuan Cui
> Sent: Friday, June 27, 2014 5:35 AM
> To: [email protected]; [email protected]; driverdev-
> [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]
> 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 <[email protected]>
> Reviewed-by: Haiyang Zhang <[email protected]>
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
>
> _______________________________________________
> devel mailing list
> [email protected]
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
Don't use likely/unlikely unless you have benchmark numbers to show that
it makes a speed up.
regards,
dan carpenter
> -----Original Message-----
> From: Dan Carpenter [mailto:[email protected]]
> Sent: Tuesday, July 8, 2014 17:27 PM
> To: Dexuan Cui
> Cc: [email protected]; [email protected]; driverdev-
> [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; Haiyang Zhang
> Subject: Re: [PATCH v2] video: hyperv: hyperv_fb: refresh the VM screen by
> force on VM panic
>
> Don't use likely/unlikely unless you have benchmark numbers to show that
> it makes a speed up.
>
> regards,
> dan carpenter
Hi Dan,
Here the variable 'synchronous_fb' is only set to true when the system panics.
So before the system panics, it's always 'unlikely'. :-)
Thanks,
-- Dexuan
On Tue, Jul 08, 2014 at 10:17:48PM +0000, Dexuan Cui wrote:
> > -----Original Message-----
> > From: Dan Carpenter [mailto:[email protected]]
> > Sent: Tuesday, July 8, 2014 17:27 PM
> > To: Dexuan Cui
> > Cc: [email protected]; [email protected]; driverdev-
> > [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; Haiyang Zhang
> > Subject: Re: [PATCH v2] video: hyperv: hyperv_fb: refresh the VM screen by
> > force on VM panic
> >
> > Don't use likely/unlikely unless you have benchmark numbers to show that
> > it makes a speed up.
> >
> > regards,
> > dan carpenter
>
> Hi Dan,
> Here the variable 'synchronous_fb' is only set to true when the system panics.
> So before the system panics, it's always 'unlikely'. :-)
Then take advantage of gcc's and your processor's prediction, which
knows that 0 is the "common" case and will choose to do the right thing
here.
Dan is right, never put those markings in your code unless you can
benchmark the difference. Which means in reality, never put them in
your code.
thanks,
gerg k-h
> -----Original Message-----
> > > From: Dan Carpenter [mailto:[email protected]]
> > > Sent: Tuesday, July 8, 2014 17:27 PM
> > > To: Dexuan Cui
> > > Cc: [email protected]; [email protected];
> driverdev-
> > > [email protected]; [email protected];
> > > [email protected]; [email protected]; [email protected];
> > > [email protected]; [email protected]; Haiyang Zhang
> > > Subject: Re: [PATCH v2] video: hyperv: hyperv_fb: refresh the VM screen
> by
> > > force on VM panic
> > >
> > > Don't use likely/unlikely unless you have benchmark numbers to show
> that
> > > it makes a speed up.
> > >
> > > regards,
> > > dan carpenter
> >
> > Hi Dan,
> > Here the variable 'synchronous_fb' is only set to true when the system
> panics.
> > So before the system panics, it's always 'unlikely'. :-)
>
> Then take advantage of gcc's and your processor's prediction, which
> knows that 0 is the "common" case and will choose to do the right thing
> here.
>
> Dan is right, never put those markings in your code unless you can
> benchmark the difference. Which means in reality, never put them in
> your code.
>
> gerg k-h
OK, let me send out a v3 patch, which will remove the unlikely.
Thanks,
-- Dexuan