[Intel-gfx] [PATCH] drm/i915: Add interface to reserve fence registers for vGPU

[Du, Changbin]

Hi chris,

On Wed, Aug 30, 2017 at 10:27:18AM +0100, Chris Wilson wrote:
> Quoting changbin.du at intel.com (2017-08-30 09:54:21)
> > This patch added two new api to the fence management code:
> >  - i915_reserve_one_fence() will try to find a free fence from fence_list
> >    and force-remove vma if need.
> >  - i915_giveback_reserved_fence() reclaim a reserved fence after vGPU has
> >    finished.
> 
> Symmetry: reserve_fence, unreserve_fence.
>
ok, I will rename the functions.

> We need a safeguard here so that the host is able to always able allocate
> to allocate a fence for the display engine. (That requirement should be
> quite soft for modern hw, nevertheless it should be in the design to
> prevent overuse from leading to an unusable system.)
> -Chris
Yes, agree. Is there any other components always need a fence ready? otherwise,
I will add a safeguard to ensure at least 1 fence register remained for host.

-- 
Thanks,
Changbin Du
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