linux-kernel - Re: [PATCH 3.16.y-ckt 030/168] drm/i915: Handle failure to kick out a conflicting fb driver

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Message-ID: <20150112174334.GI2455@charon>
Date:	Mon, 12 Jan 2015 17:43:34 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>, kernel-team@...ts.ubuntu.com,
	"Nikula, Jani" <jani.nikula@...ux.intel.com>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>
Subject: Re: [PATCH 3.16.y-ckt 030/168] drm/i915: Handle failure to kick out
 a conflicting fb driver

On Mon, Jan 12, 2015 at 06:20:22PM +0100, Daniel Vetter wrote:
> On Sun, Jan 11, 2015 at 10:49 PM, Ben Hutchings <ben@...adent.org.uk> wrote:
> > On Mon, 2014-12-15 at 14:24 +0000, Luis Henriques wrote:
> >> 3.16.7-ckt3 -stable review patch.  If anyone has any objections, please let me know.
> >>
> >> ------------------
> >>
> >> From: Chris Wilson <chris@...is-wilson.co.uk>
> >>
> >> commit f96de58fc7e7d3d717c7c63975c3b896c906b5e3 upstream.
> >>
> >> Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> >> Reviewed-by: Jani Nikula <jani.nikula@...el.com>
> >> Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
> >> Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
> >
> > Should this also be applied to any older stable branches?
> >
> > i915_kick_out_firmware_fb() was introduced in 3.6 and it has always been
> > possible for the alloc_apertures() call to fail.
> >
> > remove_conflicting_framebuffers() has returned an error code since 3.14
> > (but could silently fail before then!) so this should be applicable to
> > the 3.14 stable branch too.
> 
> tbh I don't know why this patch ended up in a stable kernel, at least
> I didn't find anything where we (drm/i915 maintainers) marked it as
> such. And there's no bugzilla references added either. Imo the patch
> doesn't qualify for stable (it's not a real-world bug afaik).

You're right, this patch was not tagged for stable.

While applying 0485c9dc24ec ("drm/i915: Kick fbdev before vgacon") to
the 3.16 kernel, I found that cherry-picking f96de58fc7e7 would make
it apply cleanly and it didn't shock me to have it in a stable kernel.
That's why I applied it for release 3.16.7-ckt3.  I guess I should
have added a note in the commit text justifying its presence.

Cheers,
--
Luís

> -Daniel
> 
> >
> > Ben.
> >
> >> ---
> >>  drivers/gpu/drm/i915/i915_dma.c | 18 +++++++++++++-----
> >>  1 file changed, 13 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> >> index d44344140627..0663fb4fa606 100644
> >> --- a/drivers/gpu/drm/i915/i915_dma.c
> >> +++ b/drivers/gpu/drm/i915/i915_dma.c
> >> @@ -1425,15 +1425,16 @@ void i915_master_destroy(struct drm_device *dev, struct drm_master *master)
> >>  }
> >>
> >>  #if IS_ENABLED(CONFIG_FB)
> >> -static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
> >> +static int i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
> >>  {
> >>       struct apertures_struct *ap;
> >>       struct pci_dev *pdev = dev_priv->dev->pdev;
> >>       bool primary;
> >> +     int ret;
> >>
> >>       ap = alloc_apertures(1);
> >>       if (!ap)
> >> -             return;
> >> +             return -ENOMEM;
> >>
> >>       ap->ranges[0].base = dev_priv->gtt.mappable_base;
> >>       ap->ranges[0].size = dev_priv->gtt.mappable_end;
> >> @@ -1441,13 +1442,16 @@ static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
> >>       primary =
> >>               pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
> >>
> >> -     remove_conflicting_framebuffers(ap, "inteldrmfb", primary);
> >> +     ret = remove_conflicting_framebuffers(ap, "inteldrmfb", primary);
> >>
> >>       kfree(ap);
> >> +
> >> +     return ret;
> >>  }
> >>  #else
> >> -static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
> >> +static int i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
> >>  {
> >> +     return 0;
> >>  }
> >>  #endif
> >>
> >> @@ -1664,7 +1668,11 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
> >>                       goto out_gtt;
> >>               }
> >>
> >> -             i915_kick_out_firmware_fb(dev_priv);
> >> +             ret = i915_kick_out_firmware_fb(dev_priv);
> >> +             if (ret) {
> >> +                     DRM_ERROR("failed to remove conflicting framebuffer drivers\n");
> >> +                     goto out_gtt;
> >> +             }
> >>       }
> >>
> >>       pci_set_master(dev->pdev);
> >
> > --
> > Ben Hutchings
> > One of the nice things about standards is that there are so many of them.
> 
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
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