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Message-ID: <20161021125729.GI4329@intel.com>
Date: Fri, 21 Oct 2016 15:57:29 +0300
From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: Daniel Vetter <daniel@...ll.ch>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org,
Noralf Trønnes <noralf@...nnes.org>,
David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] drm/fb-helper: Don't call dirty callback for untouched
clips
On Fri, Oct 21, 2016 at 02:48:49PM +0200, Takashi Iwai wrote:
> On Fri, 21 Oct 2016 14:30:32 +0200,
> Daniel Vetter wrote:
> >
> > On Thu, Oct 20, 2016 at 05:00:35PM +0200, Takashi Iwai wrote:
> > > On Thu, 20 Oct 2016 16:56:04 +0200,
> > > Ville Syrjälä wrote:
> > > >
> > > > On Thu, Oct 20, 2016 at 04:39:52PM +0200, Takashi Iwai wrote:
> > > > > Since 4.7 kernel, we've seen the error messages like
> > > > >
> > > > > kernel: [TTM] Buffer eviction failed
> > > > > kernel: qxl 0000:00:02.0: object_init failed for (4026540032, 0x00000001)
> > > > > kernel: [drm:qxl_alloc_bo_reserved [qxl]] *ERROR* failed to allocate VRAM BO
> > > > >
> > > > > on QXL when switching and accessing on VT. The culprit was the
> > > > > generic deferred_io code (qxl driver switched to it since 4.7).
> > > > > There is a race between the dirty clip update and the call of
> > > > > callback.
> > > > >
> > > > > In drm_fb_helper_dirty(), the dirty clip is updated in the spinlock,
> > > > > while it kicks off the update worker outside the spinlock. Meanwhile
> > > > > the update worker clears the dirty clip in the spinlock, too. Thus,
> > > > > when drm_fb_helper_dirty() is called concurrently, schedule_work() is
> > > > > called after the clip is cleared in the first worker call.
> > > > >
> > > > > This patch addresses it by validating the clip before calling the
> > > > > dirty fb callback.
> > > > >
> > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98322
> > > > > Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1003298
> > > > > Fixes: eaa434defaca ('drm/fb-helper: Add fb_deferred_io support')
> > > > > Cc: <stable@...r.kernel.org>
> > > > > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> > > > > ---
> > > > > drivers/gpu/drm/drm_fb_helper.c | 13 +++++++++----
> > > > > 1 file changed, 9 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > > > > index 03414bde1f15..d790d205129e 100644
> > > > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > > > @@ -636,15 +636,20 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
> > > > > dirty_work);
> > > > > struct drm_clip_rect *clip = &helper->dirty_clip;
> > > > > struct drm_clip_rect clip_copy;
> > > > > + bool dirty;
> > > > > unsigned long flags;
> > > > >
> > > > > spin_lock_irqsave(&helper->dirty_lock, flags);
> > > > > - clip_copy = *clip;
> > > > > - clip->x1 = clip->y1 = ~0;
> > > > > - clip->x2 = clip->y2 = 0;
> > > > > + dirty = (clip->x1 < clip->x2 && clip->y1 < clip->y2);
> > > > > + if (dirty) {
> > > > > + clip_copy = *clip;
> > > > > + clip->x1 = clip->y1 = ~0;
> > > > > + clip->x2 = clip->y2 = 0;
> > > > > + }
> > > > > spin_unlock_irqrestore(&helper->dirty_lock, flags);
> > > > >
> > > > > - helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
> > > > > + if (dirty)
> > > >
> > > > Could do it the other way too, ie. just make the copy, and then check the
> > > > copy (can be done after dropping the lock even). Would avoid having to
> > > > add the 'dirty' variable.
> > >
> > > Sounds good. Let me try...
> >
> > Another thing: How do we prevent userspace from doing the same, i.e.
> > submitting an empty rectangle? Do we need to patch up
> > drm_mode_dirtyfb_ioctl too? Not much point if we fix this bug in the fb
> > helpers and leave the barn door wide open for userspace to oops drivers
> > ;-)
>
> OK, then how about adding a helper to call the dirty callback with a
> sanity check like below?
>
>
> Takashi
>
> ---
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 03414bde1f15..7bef4d642511 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -644,7 +644,7 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
> clip->x2 = clip->y2 = 0;
> spin_unlock_irqrestore(&helper->dirty_lock, flags);
>
> - helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
> + drm_framebuffer_update_dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
> }
>
> /**
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 398efd67cb93..0817a0b607c5 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -529,6 +529,25 @@ int drm_mode_getfb(struct drm_device *dev,
> }
>
> /**
> + * blah blah
> + */
> +int drm_framebuffer_update_dirty(struct drm_framebuffer *fb,
> + struct drm_file *file_priv,
> + unsigned flags, unsigned color,
> + struct drm_clip_rect *clips,
> + unsigned num_clips)
> +{
> + if (!fb->funcs->dirty)
> + return -ENOSYS;
> + if (!num_clips)
> + return 0;
> + if (clips->x1 >= clips->x2 || clips->y1 >= clips->y2)
> + return 0;
Would need to check every rect here.
Also for the ANNOTATE_COPY thing, should we check that each pair
of rects has the same size?
> + return fb->funcs->dirty(fb, file_priv, flags, color, clips, num_clips);
> +}
> +EXPORT_SYMBOL(drm_framebuffer_update_dirty);
> +
> +/**
> * drm_mode_dirtyfb_ioctl - flush frontbuffer rendering on an FB
> * @dev: drm device for the ioctl
> * @data: data pointer for the ioctl
> @@ -600,12 +619,8 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev,
> }
> }
>
> - if (fb->funcs->dirty) {
> - ret = fb->funcs->dirty(fb, file_priv, flags, r->color,
> - clips, num_clips);
> - } else {
> - ret = -ENOSYS;
> - }
> + ret = drm_framebuffer_update_dirty(fb, file_priv, flags, r->color,
> + clips, num_clips);
>
> out_err2:
> kfree(clips);
> diff --git a/include/drm/drm_framebuffer.h b/include/drm/drm_framebuffer.h
> index f5ae1f436a4b..feabd9139fdb 100644
> --- a/include/drm/drm_framebuffer.h
> +++ b/include/drm/drm_framebuffer.h
> @@ -217,6 +217,12 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb);
> void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
> void drm_framebuffer_unregister_private(struct drm_framebuffer *fb);
>
> +int drm_framebuffer_update_dirty(struct drm_framebuffer *fb,
> + struct drm_file *file_priv,
> + unsigned flags, unsigned color,
> + struct drm_clip_rect *clips,
> + unsigned num_clips);
> +
> /**
> * drm_framebuffer_reference - incr the fb refcnt
> * @fb: framebuffer
--
Ville Syrjälä
Intel OTC
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