[PATCH v2 0/2] Allow partial memory mapping for cpu memory

[Andi Shyti]

Hi Matt,

On Wed, Aug 14, 2024 at 04:07:02PM +0000, Matthew Brost wrote:
> On Wed, Aug 14, 2024 at 03:48:32PM +0200, Andi Shyti wrote:
> > I am resending this patch series, not to disregard the previous
> > discussions, but to ensure it gets tested with the IGTs that
> > Krzysztof has provided.
> > 
> > This patch series finalizes the memory mapping fixes and
> > improvements by enabling partial memory mapping for CPU memory as
> > well.
> > 
> > The concept of partial memory mapping, achieved by adding an
> > object offset, was implicitly introduced in commit 8bdd9ef7e9b1
> > ("drm/i915/gem: Fix Virtual Memory mapping boundaries
> > calculation") for GTT memory.
> > 
> > To address a previous discussion with Sima and Matt, this feature
> > is used by Mesa and is required across all platforms utilizing
> > Mesa. Although Nirmoy suggested using the Fixes tag to backport
> 
> Other vendors than Intel too?

Yes, that's what I understood.

I hope Lionel can jump in and explain the use cases from Mesa
perspective.

> > this to previous kernels, I view this as a new feature rather
> > than a fix.
> > 
> > Lionel, please let me know if you have a different perspective
> > and believe this should be treated as a bug fix, requiring it
> > to be backported to stable kernels.
> > 
> > The IGTs have been developed in collaboration with the Mesa team
> > to replicate the exact Mesa use case[*].
> > 
> > Thanks Chris for the support, thanks Krzysztof for taking care of
> > the IGT tests, thanks Nirmoy for your reviews and thanks Sima and
> > Matt for the discussion on this series.
> > 
> > Andi
> > 
> > [*] https://patchwork.freedesktop.org/patch/608232/?series=137303&rev=1
> 
> So here is really quick test [1] which I put together in Xe to test
> partial mmaps, not as complete as the i915 one though.
> 
> It fails on the Xe baseline.
> 
> It pass if with [2] in drm_gem.c:drm_gem_mmap. Blindly changing that
> function might not be the correct solution but thought I'd share as a
> reference.

Thanks for sharing it. I took a quick look and I think there are
a few things missing there. If you want and if this is not in
anyone's task list, I can try to "port" this in XE.

Is there any other objection to getting this merged into i915?

Andi