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Date:   Sun, 03 May 2020 21:30:21 +0100
From:   Chris Wilson <>
To:     "Jason A. Donenfeld" <>,,,,,
Cc:     "Jason A. Donenfeld" <>,
Subject: Re: [PATCH] drm/i915: check to see if SIMD registers are available before using SIMD

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:

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.

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