[PATCH 7/7 v2] drm/radeon: Refuse to migrate a prime BO to VRAM. (v2)

[Christopher James Halse Rogers]

I also haven't tested it on hardware (all my hardware seems to be supported
by amdgpu), but the only times we touch prime_shared_count are:
1) It's set to 1 in radeon_gem_prime_import_sg_table. This shouldn't be
called in the self-import case (and isn't, as far as I can tell), and
2) It's incremented in radeon_gem_prime_pin, right after the bo is pinned
to GTT, so cannot be migrated to VRAM anyway (unless there's an unmatched
radeon_bo_unpin call somewhere else?).

On Tue, 4 Apr 2017 at 02:30 Christian König <deathsimple at vodafone.de> wrote:

> Am 03.04.2017 um 17:51 schrieb Alex Deucher:
> > On Mon, Apr 3, 2017 at 4:24 AM, Christian König <deathsimple at vodafone.de>
> wrote:
> >> Am 03.04.2017 um 05:35 schrieb raof at ubuntu.com:
> >>> From: Christopher James Halse Rogers
> >>> <christopher.halse.rogers at canonical.com>
> >>>
> >>> BOs shared via dma-buf, either imported or exported, cannot sensibly be
> >>> migrated to VRAM
> >>> without breaking the dma-buf sharing. Refuse userspace requests to
> migrate
> >>> to VRAM,
> >>> ensure such BOs are not migrated during command submission, and refuse
> to
> >>> pin them
> >>> to VRAM.
> >>>
> >>> v2: Don't pin BOs in GTT. Instead, refuse to migrate BOs to VRAM.
> >>>
> >>> Signed-off-by: Christopher James Halse Rogers
> >>> <christopher.halse.rogers at canonical.com>
> >>
> >> Patches #4, #6 and this one (#7) are Reviewed-by: Christian König
> >> <christian.koenig at amd.com>.
> > Will this cause any issues with self sharing?  E.g., the standard use
> > case with a single GPU and DRI3?
>
> No, the code from amdgpu to count the number of times we really shared a
> BO with somebody was ported over to radeon as far as I can see.
>
> So that should work fine, but I haven't double checked or tested it.
>
> Christian.
>
> >
> > Alex
> >
> >>
> >>> ---
> >>>    drivers/gpu/drm/radeon/radeon_cs.c     | 10 ++++++++++
> >>>    drivers/gpu/drm/radeon/radeon_gem.c    |  4 ++++
> >>>    drivers/gpu/drm/radeon/radeon_object.c |  5 +++++
> >>>    3 files changed, 19 insertions(+)
> >>>
> >>> diff --git a/drivers/gpu/drm/radeon/radeon_cs.c
> >>> b/drivers/gpu/drm/radeon/radeon_cs.c
> >>> index a8442f7196d6..df6b58c08544 100644
> >>> --- a/drivers/gpu/drm/radeon/radeon_cs.c
> >>> +++ b/drivers/gpu/drm/radeon/radeon_cs.c
> >>> @@ -164,6 +164,16 @@ static int radeon_cs_parser_relocs(struct
> >>> radeon_cs_parser *p)
> >>>                          p->relocs[i].allowed_domains = domain;
> >>>                  }
> >>>    +             /* Objects shared as dma-bufs cannot be moved to VRAM
> */
> >>> +               if (p->relocs[i].robj->prime_shared_count) {
> >>> +                       p->relocs[i].allowed_domains &=
> >>> ~RADEON_GEM_DOMAIN_VRAM;
> >>> +                       if (!p->relocs[i].allowed_domains) {
> >>> +                               DRM_ERROR("BO associated with dma-buf
> >>> cannot "
> >>> +                                         "be moved to VRAM\n");
> >>> +                               return -EINVAL;
> >>> +                       }
> >>> +               }
> >>> +
> >>>                  p->relocs[i].tv.bo = &p->relocs[i].robj->tbo;
> >>>                  p->relocs[i].tv.shared = !r->write_domain;
> >>>    diff --git a/drivers/gpu/drm/radeon/radeon_gem.c
> >>> b/drivers/gpu/drm/radeon/radeon_gem.c
> >>> index 96683f5b2b1b..067ea7d7658a 100644
> >>> --- a/drivers/gpu/drm/radeon/radeon_gem.c
> >>> +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> >>> @@ -120,6 +120,10 @@ static int radeon_gem_set_domain(struct
> >>> drm_gem_object *gobj,
> >>>                          return r;
> >>>                  }
> >>>          }
> >>> +       if (domain == RADEON_GEM_DOMAIN_VRAM &&
> robj->prime_shared_count)
> >>> {
> >>> +               /* A BO that is associated with a dma-buf cannot be
> >>> sensibly migrated to VRAM */
> >>> +               return -EINVAL;
> >>> +       }
> >>>          return 0;
> >>>    }
> >>>    diff --git a/drivers/gpu/drm/radeon/radeon_object.c
> >>> b/drivers/gpu/drm/radeon/radeon_object.c
> >>> index 74b276060c20..bec2ec056de4 100644
> >>> --- a/drivers/gpu/drm/radeon/radeon_object.c
> >>> +++ b/drivers/gpu/drm/radeon/radeon_object.c
> >>> @@ -352,6 +352,11 @@ int radeon_bo_pin_restricted(struct radeon_bo *bo,
> >>> u32 domain, u64 max_offset,
> >>>                  return 0;
> >>>          }
> >>> +       if (bo->prime_shared_count && domain ==
> RADEON_GEM_DOMAIN_VRAM) {
> >>> +               /* A BO shared as a dma-buf cannot be sensibly
> migrated to
> >>> VRAM */
> >>> +               return -EINVAL;
> >>> +       }
> >>> +
> >>>          radeon_ttm_placement_from_domain(bo, domain);
> >>>          for (i = 0; i < bo->placement.num_placement; i++) {
> >>>                  /* force to pin into visible video ram */
> >>
> >>
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