On Fri, May 1, 2020 at 12:07 PM Christoph Hellwig hch@infradead.org wrote:

On Thu, Apr 30, 2020 at 04:10:16PM -0600, Jason A. Donenfeld wrote:

...

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.

Err, why does i915 implements its own uncached memcpy instead of relying on core functionality to start with?

I was wondering the same. It sure does seem like this ought to be more generalized functionality, with a name that represents the type of transfer it's optimized for (wc or similar).