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

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Daniel,

On Mon, Aug 12, 2024 at 11:11:21AM +0200, Daniel Vetter wrote:
> On Fri, Aug 09, 2024 at 11:20:56AM +0100, Andi Shyti wrote:
> > On Fri, Aug 09, 2024 at 10:53:38AM +0200, Daniel Vetter wrote:
> > > On Wed, Aug 07, 2024 at 11:05:19AM +0100, Andi Shyti wrote:
> > > > This patch series concludes on the memory mapping fixes and
> > > > improvements by allowing partial memory mapping for the cpu
> > > > memory as well.
> > > > 
> > > > The partial memory mapping by adding an object offset was
> > > > implicitely included in commit 8bdd9ef7e9b1 ("drm/i915/gem: Fix
> > > > Virtual Memory mapping boundaries calculation") for the gtt
> > > > memory.
> > > 
> > > Does userspace actually care? Do we have a flag or something, so that
> > > userspace can discover this?
> > > 
> > > Adding complexity of any kind is absolute no-go, unless there's a
> > > userspace need. This also includes the gtt accidental fix.
> > 
> > Actually this missing functionality was initially filed as a bug
> > by mesa folks. So that this patch was requested by them (Lionel
> > is Cc'ed).
> > 
> > The tests cases that have been sent previously and I'm going to
> > send again, are directly taken from mesa use cases.
> 
> Please add the relevant mesa MR to this patch then, and some relevant
> explanations for how userspace detects this all and decides to use it.

AFAIK, there is no Mesa MR. We are adding a feature that was
missing, but Mesa already supported it (indeed, Nimroy suggested
adding the Fixes tag for this).

Also because, Mesa was receiving an invalid address error and
asked to support the partial mapping of the memory.

> Also, does xe also support this? If we only add this to i915-gem but xe
> doesn't have it, it doesn't make much sense imo.

I don't know about. Lionel, Do you have anything to add here from
your side?

Thanks,
Andi