From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753837Ab2EaUng (ORCPT ); Thu, 31 May 2012 16:43:36 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:20350 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951Ab2EaUnf (ORCPT ); Thu, 31 May 2012 16:43:35 -0400 Date: Thu, 31 May 2012 16:35:44 -0400 From: Konrad Rzeszutek Wilk To: "H. Peter Anvin" Cc: konrad@darnok.org, linux-kernel@vger.kernel.org, x86@kernel.org, mingo@redhat.com, tglx@linutronix.de, stable@kernel.org Subject: Re: [PATCH] x86/i386: Check PSE bit before using PAGE_KERNEL_LARGE. Message-ID: <20120531203544.GA19420@phenom.dumpdata.com> References: <1338493218-25006-1-git-send-email-konrad.wilk@oracle.com> <4FC7D2AE.9080603@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FC7D2AE.9080603@zytor.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 31, 2012 at 01:21:02PM -0700, H. Peter Anvin wrote: > On 05/31/2012 12:40 PM, Konrad Rzeszutek Wilk wrote: > > During bootup we would unconditionally do this on any > > machine that was built with CONFIG_NUMA=y on i386: > > > > setup_arch > > \-initmem_init > > \-x86_numa_init (with dummy_init as callback) > > \- init_alloc_remap > > \- set_pmd_pfn (with PAGE_PSE) > > > > without checking to see if the CPU supports PSE. This > > patch adds that and also allows the init_alloc_remap function > > to properly work by falling back on PTEs. > > > > Well, the code looks like it is PAE-specific, and PAE implies PSE. I have to double check - but I think a kernel built with CONFIG_HIGHMEM64=y and CONFIG_NUMA=y would boot on a Pentium II which can't do PAE. But perhaps there are some other checks that would halt the kernel before it even got there? > > Xen breaks that, but that is a divergence of Xen from x86. It certainly does . And that is how I spotted this - b/c the PMD would fail (with tons of mutlicalls warnings) - and the PTE's would still point to the old PFNs.