From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [SeaBIOS] [PATCH] Make MTRR region 0xc0000-0x100000 be cached. Date: Sun, 03 Jan 2010 08:15:31 +0200 Message-ID: <4B403603.80504@redhat.com> References: <20100101182308.GB10271@morn.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: seabios@seabios.org, kvm@vger.kernel.org To: "Kevin O'Connor" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62456 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750782Ab0ACGPs (ORCPT ); Sun, 3 Jan 2010 01:15:48 -0500 In-Reply-To: <20100101182308.GB10271@morn.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: On 01/01/2010 08:23 PM, Kevin O'Connor wrote: > The current MTRR code in SeaBIOS uses uncached ram for > 0xc0000-0x100000. This seems overly pessimistic as "write protect" > should be sufficient. (Note, a WP mtrr does not prevent writes - it > is a caching strategy for memory that can be read-only.) > > I'm not sure how much KVM really uses the MTRRs, but if it does honor > them this should make bootup a bit faster as it will allow caching of > the SeaBIOS code. > > This change also clears all the variable mtrrs, and makes sure all the > mtrrs are set before they are enabled. > > kvm ignores the MTRRs, unless device assignment is enabled, in which case it honours them. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.