[Intel-gfx] [PATCH 136/190] drm/i915: Move ioremap_wc tracking onto VMA

[Tvrtko Ursulin]

On 11/02/16 13:29, Chris Wilson wrote:
> On Thu, Feb 11, 2016 at 01:20:46PM +0000, Tvrtko Ursulin wrote:
>>
>>
>> On 11/01/16 10:45, Chris Wilson wrote:
>>> By tracking the iomapping on the VMA itself, we can share that area
>>> between multiple users. Also by only revoking the iomapping upon
>>> unbinding from the mappable portion of the GGTT, we can keep that iomap
>>> across multiple invocations (e.g. execlists context pinning).
>>
>> Between the lines and from some IRC discussion it seems the goal of
>> this is to fix an address space memory leak with fbcon?
>
> The goal is to prevent an issue from hastily dropping iomappings (and
> vmappings elsewhere) when unpinning contexts. That comes into play when
> we track the ring->vma (not just track ring->vma as we do now, but can
> rely on the vma being persistent). Fixing a leak on driver unload is an
> interesting side-effect.
>
>> But I don't know fbdev so can't find who would do the unpin on the
>> VMA to allow unbind to eventually unmap it?
>
> That actually gets fixed in another patch when we teach intel_fbdev to
> actually track the VMA it allocates, as right now we deliberately leak
> it to keep the code simple.

Ok in that case ack on the patch.

It will need to assert on VMA being pinned I think and some minor 
changes when you rebase it on top of nightly as standalone so I can 
properly review it then.

Regards,

Tvrtko