From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753822AbcHRLM4 convert rfc822-to-8bit (ORCPT ); Thu, 18 Aug 2016 07:12:56 -0400 Received: from prv-mh.provo.novell.com ([137.65.248.74]:54740 "EHLO prv-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752483AbcHRLMz (ORCPT ); Thu, 18 Aug 2016 07:12:55 -0400 Message-Id: <57B5B4560200007800107092@prv-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.2.1 Date: Thu, 18 Aug 2016 05:12:54 -0600 From: "Jan Beulich" To: "Andrew Cooper" , "Konrad Rzeszutek Wilk" Cc: , , "xen-devel" , "Boris Ostrovsky" , , "Juergen Gross" , Subject: Re: [Xen-devel] XSA 154 and ISA region (640K -> 1MB) WB cache instead of UC References: <20160817203238.GA9408@char.us.oracle.com> <57B5A4C90200007800106FF2@prv-mh.provo.novell.com> <47fabc70-4500-1035-7dc7-7f0a3915471f@citrix.com> In-Reply-To: <47fabc70-4500-1035-7dc7-7f0a3915471f@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 18.08.16 at 12:16, wrote: > On 18/08/16 11:06, Jan Beulich wrote: >>>>> On 17.08.16 at 22:32, wrote: >>> Looking at the kernel it assumes that WB is ok for 640KB->1MB. >>> The comment says: >>> " /* Low ISA region is always mapped WB in page table. No need to track > *" >> As per above it's not clear to me what this comment is backed by. > > This states what is in the pagetables. Not the combined result with MTRRs. > > WB in the pagetables and WC/UB in the MTRRs is a legal combination which > functions correctly. True, but then again - haven't I been told multiple times that Linux nowadays prefers to run without using MTRRs? Jan