Re: [PATCH v2 2/2] drm/i915: Invalidate the guc ggtt TLB upon insertion

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On 01/12/2016 10:57, Chris Wilson wrote:
On Thu, Dec 01, 2016 at 10:49:31AM +0000, Tvrtko Ursulin wrote:

On 01/12/2016 10:26, Chris Wilson wrote:
On Thu, Dec 01, 2016 at 10:06:25AM +0000, Tvrtko Ursulin wrote:

On 01/12/2016 09:46, Chris Wilson wrote:
Move the GuC invalidation of its ggtt TLB to where we perform the ggtt
modification rather than proliferate it into all the callers of the
insert (which may or may not in fact have to do the insertion).

v2: Just do the guc invalidate unconditionally, (afaict) it has no impact
without the guc loaded on gen8+

Why do you find it tempting to do it unconditionally? I would rather
not touch it on gen8 at all and would also prefer the conditional
flush in gen9.

Because if I add a conditional here, I end up wanting writing a new vfunc
for invalidate (if I can coax the gmch / gen6 / guc usage into something
consistent). And I'm lazy. :)

To make sure I fully understand - just because you would not like to
see the conditional in gen8_ggtt_invalidate? So you would add
gen8_ggtt_invalidate and gen9_ggtt_invalidate with a GuC flush?

gen9_guc_ggtt_invalidate. Because I don't like the conditional in
i915_ggtt_flush() - and that shows we have another place missing the guc
invalidate. And also because at one point, I was toying with
the idea of pushing the flush out to the caller of ->insert_page() in
case they wanted to manipulate multiple pages. (However, that looks
like it will remain single pages only.) I

I would have thought conditional is less bothersome than making the
unused piece of the GPU (on gen8) do stuff.

I thought you wouldn't want to punch a bit on the register if it wasn't
being used at all.

Yes I wouldn't, and not only unused but not validated probably.

Regards,

Tvrtko
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