Re: [git pull] drm for 3.19-rc1

[Dave Airlie]

On 16 December 2014 at 10:35, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Sun, Dec 14, 2014 at 11:17 PM, Dave Airlie <airlied@xxxxxxxx> 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.

Dave.
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