From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@infradead.org>,
Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"intel-gfx@lists.freedesktop.org"
<intel-gfx@lists.freedesktop.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"bigeasy@linutronix.de" <bigeasy@linutronix.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH] drm/i915: check to see if SIMD registers are available before using SIMD
Date: Mon, 4 May 2020 16:15:41 +0000 [thread overview]
Message-ID: <cb9e8125a94e4efc8733967a5b47be88@AcuMS.aculab.com> (raw)
In-Reply-To: <20200504160314.GA26373@infradead.org>
From: Christoph Hellwig
> Sent: 04 May 2020 17:03
>
> On Sun, May 03, 2020 at 09:20:19PM +0100, Chris Wilson wrote:
> > > Err, why does i915 implements its own uncached memcpy instead of relying
> > > on core functionality to start with?
> >
> > What is this core functionality that provides movntqda?
>
> A sensible name might be memcpy_uncached or mempcy_nontemporal.
> But the important point is that this should be arch code with a common
> fallback rather than hacking it up in drivers.
More the point, you are trying to do a copy where:
1) The kernel isn't expected to read the data - so can bypass the cache.
and maybe:
2) The data needs flushing from the cache to actual memory.
and maybe:
3) The cache lines need invalidating.
The fallbacks depend on the required behaviour.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-05-04 16:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 22:10 Jason A. Donenfeld
2020-05-01 10:42 ` Sebastian Andrzej Siewior
2020-05-01 11:34 ` David Laight
2020-05-01 21:54 ` Jason A. Donenfeld
2020-05-01 18:07 ` Christoph Hellwig
2020-05-01 21:55 ` Jason A. Donenfeld
2020-05-03 20:20 ` Chris Wilson
2020-05-04 16:03 ` Christoph Hellwig
2020-05-04 16:15 ` David Laight [this message]
2020-05-03 20:30 ` Chris Wilson
2020-05-03 20:35 ` Jason A. Donenfeld
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