linux-kernel - Re: [git pull] drm for 3.19-rc1

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Message-ID: <CAF6AEGvib-pnowM1pbTNt9Y-ZDuqAxrbm+aZS9+HWvWskEqpxA@mail.gmail.com>
Date:	Mon, 15 Dec 2014 20:48:22 -0500
From:	Rob Clark <robdclark@...il.com>
To:	Dave Airlie <airlied@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Hellstrom <thellstrom@...are.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	DRI mailing list <dri-devel@...ts.freedesktop.org>,
	Alex Deucher <alexander.deucher@....com>,
	Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [git pull] drm for 3.19-rc1

On Mon, Dec 15, 2014 at 7:48 PM, Dave Airlie <airlied@...il.com> wrote:
> On 16 December 2014 at 10:35, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>> On Sun, Dec 14, 2014 at 11:17 PM, Dave Airlie <airlied@...ux.ie> wrote:
>>>
>>> i915:
>>>         Initial Skylake (SKL) support
>>>         gen3/4 reset work
>>>         start of dri1/ums removal
>>>         infoframe tracking
>>>         fixes for lots of things.
>>
>> So I'm not sure how happy I am about this. It seems to work, but on
>> the very first boot I get this:
>>
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 1 PID: 1292 at
>> drivers/gpu/drm/i915/i915_gem_execbuffer.c:125
>> eb_lookup_vmas.isra.18+0x333/0x3d0 [i915]()
>>   GPU use of dumb buffer is illegal.
>>   Modules linked in: ip6t_rpfilter bnep ip6t_REJECT nf_reject_ipv6
>> bluetooth nf_conntrack_ipv6 ...
>>    video
>>   CPU: 1 PID: 1292 Comm: Xorg Not tainted 3.18.0-09423-g988adfdffdd4 #1
>>   Hardware name:                  /DH87RL, BIOS
>> RLH8710H.86A.0327.2014.0924.1645 09/24/2014
>>   Call Trace:
>>     dump_stack+0x45/0x57
>>     warn_slowpath_common+0x80/0xc0
>>     warn_slowpath_fmt+0x41/0x50
>>     ? sg_kfree+0x30/0x30
>>     eb_lookup_vmas.isra.18+0x333/0x3d0 [i915]
>>     i915_gem_do_execbuffer.isra.25+0x50d/0xd80 [i915]
>>     ? unlock_page+0x6d/0x80
>>     i915_gem_execbuffer2+0xb1/0x2c0 [i915]
>>     drm_ioctl+0x19c/0x630 [drm]
>>     do_vfs_ioctl+0x2e0/0x4e0
>>     ? file_has_perm+0x87/0xa0
>>     ? __audit_syscall_entry+0xac/0x100
>>     SyS_ioctl+0x81/0xa0
>>     ? do_page_fault+0xc/0x10
>>     system_call_fastpath+0x12/0x17
>>   ---[ end trace cb3c78163212ca1d ]---
>>
>> apparently Introduced by commit 355a70183848 ("drm/gem: Warn on
>> illegal use of the dumb buffer interface v2")
>>
>> The commit says "the next step is to fail".
>>
>> And I want to make it painfully clear that if somebody breaks existing
>> working setups, they don't get to work on the kernel.
>>
>> So get rid of the warning. And get rid of the notion that you can just
>> fail. You can try to fix Xorg, and then come back to this - in a
>> couple of years - when it no longer happens.
>>
>
> I'd be inclined to just revert this for now, it is annoying we let
> userspace away with this, but we probably need to find a better
> way to enforce it, since the cat is out of the bag.

Replace w/ DRM_ERROR?  (perhaps ratelimited..)?

It's not a driver error, so much as a warning for userspace that it is
doing something that is not expected to work on all hw / generations,
and it appears to be finding more or less what it was intended to
find, although I'm not sure the stack trace serves much purpose.

BR,
-R

> Dave.
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
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