Re: [PATCH 3/8] drm/amdgpu: Implement mmap as GEM object function

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Hi

Am 07.04.21 um 21:49 schrieb Felix Kuehling:
> On 2021-04-07 3:34 p.m., Felix Kuehling wrote:
> > On 2021-04-07 7:25 a.m., Christian König wrote:
> > > > > > > +    /*
> > > > > > > +     * Don't verify access for KFD BOs. They don't have a GEM
> > > > > > > +     * object associated with them.
> > > > > > > +     */
> > > > > > > +    if (bo->kfd_bo)
> > > > > > > +        goto out;
> > > > > > Who does the access verification now?
> > > > > This is somewhat confusing.
> > > > >
> > > > > I took this check as-is, including the comment, from amdgpu's
> > > > > verify_access function. The verify_access function was called by
> > > > > ttm_bo_mmap. It returned 0 and ttm_bo_mmap did the mapping.
> > > > This is probably a left-over from when we mapped BOs using /dev/kfd. We
> > > > changed this to use /dev/dri/renderD* a long time ago to fix CPU 
> > > > mapping
> > > > invalidations on memory evictions. I think we can let GEM do the access
> > > > check.
> > >
> > > Ok, good to know.
> > >
> > > Thomas can you remove the extra handling in a separate prerequisite 
> > > patch?
> > >
> > > If anybody then bisects to this patch we at least know what to do to 
> > > get it working again.
> >
> > FWIW, I ran KFDTest test with this shortcut removed on current 
> > amd-staging-drm-next + my HMM patch series, and it didn't seem to 
> > cause any issues.
>
> Wait, I celebrated too soon. I was running the wrong kernel. I do see 
> some failures where access is being denied. I need to do more debugging 
> to figure out what's causing that.

OK, thanks for looking into this. I'll wait a bit before sending out the 
new patchset.

Best regards
Thomas

> Regards,
>    Felix
>
>
> > Regards,
> >   Felix
> >
> >
> > > Regards,
> > > Christian. 

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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