[Intel-gfx] [Linaro-mm-sig] [PATCH 1/2] dma-buf.rst: Document why indefinite fences are a bad idea

[Daniel Vetter]

On Mon, Jul 20, 2020 at 01:15:17PM +0200, Thomas Hellström (Intel) wrote:
> Hi,
> 
> On 7/9/20 2:33 PM, Daniel Vetter wrote:
> > Comes up every few years, gets somewhat tedious to discuss, let's
> > write this down once and for all.
> > 
> > What I'm not sure about is whether the text should be more explicit in
> > flat out mandating the amdkfd eviction fences for long running compute
> > workloads or workloads where userspace fencing is allowed.
> 
> Although (in my humble opinion) it might be possible to completely untangle
> kernel-introduced fences for resource management and dma-fences used for
> completion- and dependency tracking and lift a lot of restrictions for the
> dma-fences, including prohibiting infinite ones, I think this makes sense
> describing the current state.

Yeah I think a future patch needs to type up how we want to make that
happen (for some cross driver consistency) and what needs to be
considered. Some of the necessary parts are already there (with like the
preemption fences amdkfd has as an example), but I think some clear docs
on what's required from both hw, drivers and userspace would be really
good.
>
> Reviewed-by: Thomas Hellstrom <thomas.hellstrom at intel.com>

Thanks for taking a look, first 3 patches here with annotations and docs
merged to drm-misc-next. I'll ask Maarten/Dave whether another pull is ok
for 5.9 so that everyone can use this asap.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch