From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267466AbUH0U1G (ORCPT ); Fri, 27 Aug 2004 16:27:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267470AbUH0UNG (ORCPT ); Fri, 27 Aug 2004 16:13:06 -0400 Received: from mx1.redhat.com ([66.187.233.31]:26563 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S267502AbUH0UEl (ORCPT ); Fri, 27 Aug 2004 16:04:41 -0400 Date: Fri, 27 Aug 2004 13:04:15 -0700 From: "David S. Miller" To: Dave Airlie Cc: torvalds@osdl.org, linux-kernel@vger.kernel.org, arjanv@redhat.com Subject: Re: drm fixup 2/2 - optimise i8x0 accesses.. Message-Id: <20040827130415.754d4451.davem@redhat.com> In-Reply-To: References: X-Mailer: Sylpheed version 0.9.12 (GTK+ 1.2.10; sparc-unknown-linux-gnu) X-Face: "_;p5u5aPsO,_Vsx"^v-pEq09'CU4&Dc1$fQExov$62l60cgCc%FnIwD=.UF^a>?5'9Kn[;433QFVV9M..2eN.@4ZWPGbdi<=?[:T>y?SD(R*-3It"Vj:)"dP Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Aug 2004 15:13:54 +0100 (IST) Dave Airlie wrote: > the patch below optimises the drm code to not do put_user() on memory the > kernel allocated and then mmap-installed to userspace, but instead makes it > use the kernel virtual address directly instead. This might cause major problems on systems with virtually indexed caches if precautions are not made at buffer allocation time such that the virtual cache color of the kernel mapping is the same as the user mapping. Arjan, you should know better :-) I also don't understand what this "optimization" is? You don't need a verify_area, therefore you can use __put_user() which amounts to a load/store and an integer move instruction.