From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: MTRR use in drivers Date: Sun, 23 Jun 2013 13:38:46 -0700 Message-ID: <51C75CD6.5010206@zytor.com> References: <51C3DDFA.7050204@zytor.com> <51C69732.1010906@gmail.com> <20130623192936.GA28655@khazad-dum.debian.net> <51C75465.9060007@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dave Airlie Cc: Henrique de Moraes Holschuh , Brice Goglin , Linux Kernel Mailing List , David Airlie , dri-devel@lists.freedesktop.org, Andy Lutomirski List-Id: dri-devel@lists.freedesktop.org On 06/23/2013 01:30 PM, Dave Airlie wrote: >>>> Why do you care about performance when PAT is disabled? > > breaking old boxes just because, is just going to get reverted when I > get the first regression report that you broke old boxes. > Not "just because", but *if* the choice is between breaking old boxes and breaking new boxes I'll take the latter. > Andy Lutomirski just submitted a bunch of patches to clean up the DRM > usage of mtrrs, they are in drm-next, afaik we no longer add them on > PAT systems. Fantastic news. No issue, then, and no need to break anything. The only problem I see with having ioremap_wc() installing an MTRR on non-PAT, rather than pushing that into the drivers which is clearly not the right thing, is that we will need a hook to uninstall it when the mapping is destroyed. -hpa