From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932359AbbICOu7 (ORCPT ); Thu, 3 Sep 2015 10:50:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:56801 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932278AbbICOu5 (ORCPT ); Thu, 3 Sep 2015 10:50:57 -0400 Subject: Re: [PATCH] xen/p2m: fix extra memory regions accounting To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , linux-kernel@vger.kernel.org References: <1441281916-38284-1-git-send-email-roger.pau@citrix.com> <55E83C46.8010701@suse.com> <55E85B61.4070203@citrix.com> Cc: Konrad Rzeszutek Wilk , Boris Ostrovsky , David Vrabel , xen-devel@lists.xenproject.org From: Juergen Gross Message-ID: <55E85E4E.5060508@suse.com> Date: Thu, 3 Sep 2015 16:50:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <55E85B61.4070203@citrix.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/2015 04:38 PM, Roger Pau Monné wrote: > El 03/09/15 a les 14.25, Juergen Gross ha escrit: >> On 09/03/2015 02:05 PM, Roger Pau Monne wrote: >>> On systems with memory maps with ranges that don't end at page >>> boundaries, >>> like: >>> >>> [...] >>> (XEN) 0000000000100000 - 00000000dfdf9c00 (usable) >>> (XEN) 00000000dfdf9c00 - 00000000dfe4bc00 (ACPI NVS) >>> [...] >>> >>> xen_add_extra_mem will create a protected range that ends up at >>> 0xdfdf9c00, >>> but the function used to check if a memory address is inside of a >>> protected >>> range works with pfns, which means that an attempt to map 0xdfdf9c00 >>> will be >>> refused because the check is performed against 0xdfdf9000 instead of >>> 0xdfdf9c00. >>> >>> In order to fix this, make sure that the ranges that are added to the >>> xen_extra_mem array are aligned to page boundaries. >>> >>> Signed-off-by: Roger Pau Monné >>> Cc: Konrad Rzeszutek Wilk >>> Cc: Boris Ostrovsky >>> Cc: David Vrabel >>> Cc: Juergen Gross >>> Cc: xen-devel@lists.xenproject.org >>> --- >>> AFAICT this patch needs to be backported to 3.19, 4.0, 4.1 and 4.2. >>> --- >>> arch/x86/xen/setup.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c >>> index 55f388e..dcf5865 100644 >>> --- a/arch/x86/xen/setup.c >>> +++ b/arch/x86/xen/setup.c >>> @@ -68,6 +68,9 @@ static void __init xen_add_extra_mem(phys_addr_t >>> start, phys_addr_t size) >>> { >>> int i; >>> >>> + start = PAGE_ALIGN(start); >>> + size &= PAGE_MASK; >> >> This is not correct. If start wasn't page aligned and size was, you'll >> add one additional page to xen_extra_mem. > > I'm not understanding this, let's put an example: > > start = 0x8c00 > size = 0x1000 > > After the fixup added above this would become: > > start = 0x9000 > size = 0x1000 > > So if anything, I'm adding one page less (because 0x8000 was partly > added, and with the fixup it is not added). You'd add 9c00-9cff which shouldn't be added (in this example you shouldn't add anything as no complete page is covered by the range). You need something like: end = (start + size) & PAGE_MASK; start = PAGE_ALIGN(start); size = end - start; if (!size) return; Juergen