[PATCH 2/2] drm/amdgpu: Enable clear page functionality

[Michel Dänzer]

On 2023-12-13 16:39, Felix Kuehling wrote:
> On 2023-12-13 9:20, Christian König wrote:
>> Am 12.12.23 um 00:32 schrieb Felix Kuehling:
>>> On 2023-12-11 04:50, Christian König wrote:
>>>> Am 08.12.23 um 20:53 schrieb Alex Deucher:
>>>>> [SNIP]
>>>>>> You also need a functionality which resets all cleared blocks to
>>>>>> uncleared after suspend/resume.
>>>>>>
>>>>>> No idea how to do this, maybe Alex knows of hand.
>>>>> Since the buffers are cleared on creation, is there actually anything to do?
>>>>
>>>> Well exactly that's the problem, the buffers are no longer always cleared on creation with this patch.
>>>>
>>>> Instead we clear on free, track which areas are cleared and clear only the ones which aren't cleared yet on creation.
>>>
>>> The code I added for clearing-on-free a long time ago, does not clear to 0, but to a non-0 poison value. That was meant to make it easier to catch applications incorrectly relying on 0-initialized memory. Is that being changed? I didn't see it in this patch series.
>>
>> Yeah, Arun stumbled over that as well. Any objections that we fill with zeros instead or is that poison value something necessary for debugging?
> 
> I don't think it's strictly necessary. But it may encourage sloppy user mode programming to rely on 0-initialized memory that ends up breaking in corner cases or on older kernels.

>From a security PoV, the kernel should never return uncleared memory to (at least unprivileged) user space. This series seems like a big step in that direction.


-- 
Earthling Michel Dänzer            |                  https://redhat.com
Libre software enthusiast          |         Mesa and Xwayland developer