On Wed, 27 Oct 2021 at 09:36, Thomas Hellström thomas.hellstrom@linux.intel.com wrote:

GPU relocs are gone. There should be no need for this workaround anymore. Remove it.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

I was completely wrong here, sorry. Digging through the git history it looks like this came from:

Commit 149c84077fe717af883bae459623ef1cebd86388 Author: Daniel Vetter daniel.vetter@ffwll.ch Date: Wed Feb 15 23:50:23 2012 +0100

drm/i915: implement SNB workaround for lazy global gtt

PIPE_CONTROL on snb needs global gtt mappings in place to workaround a hw gotcha. No other commands need such a workaround. Luckily we can detect a PIPE_CONTROL commands easily because they have a write_domain = I915_GEM_DOMAIN_INSTRUCTION (and nothing else has that).

so it looks to be unrelated to GPU relocs, which AFAIK didn't exist at the time. I just saw the MI comment and assumed it was talking about the MI_STORE_DWORD...

---

.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 19 +------------------ 1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 1231224728e4..04af88e6d453 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -1327,7 +1327,6 @@ eb_relocate_entry(struct i915_execbuffer *eb, { struct drm_i915_private *i915 = eb->i915; struct eb_vma *target;

•   int err;
  
    /* we've already hold a reference to all valid objects */
    target = eb_get_vma(eb, reloc->target_handle);
  

@@ -1357,25 +1356,9 @@ eb_relocate_entry(struct i915_execbuffer *eb, return -EINVAL; }

•   if (reloc->write_domain) {
  

•   if (reloc->write_domain)
            target->flags |= EXEC_OBJECT_WRITE;
  
  

•           /*
  

•            * Sandybridge PPGTT errata: We need a global gtt mapping
  

•            * for MI and pipe_control writes because the gpu doesn't
  

•            * properly redirect them through the ppgtt for non_secure
  

•            * batchbuffers.
  

•            */
  

•           if (reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&
  

•               GRAPHICS_VER(eb->i915) == 6) {
  

•                   err = i915_vma_bind(target->vma,
  

•                                       target->vma->obj->cache_level,
  

•                                       PIN_GLOBAL, NULL);
  

•                   if (err)
  

•                           return err;
  

•           }
  

•   }
  

•   /*
     * If the relocation already has the right value in it, no
     * more work needs to be done.
  

-- 2.31.1