Re: [PATCH] drm/i915: check to see if SIMD registers are available before using SIMD

[Jason A. Donenfeld]

On Sun, May 3, 2020 at 2:30 PM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
>
> Quoting Jason A. Donenfeld (2020-04-30 23:10:16)
> > Sometimes it's not okay to use SIMD registers, the conditions for which
> > have changed subtly from kernel release to kernel release. Usually the
> > pattern is to check for may_use_simd() and then fallback to using
> > something slower in the unlikely case SIMD registers aren't available.
> > So, this patch fixes up i915's accelerated memcpy routines to fallback
> > to boring memcpy if may_use_simd() is false.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
>
> The same argument as on the previous submission is that we return to the
> caller if we can't use movntqda as their fallback path should be faster
> than uncached memcpy.

Oh, THAT's what you meant before. Okay, will follow up.