From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933529AbbICP5O (ORCPT ); Thu, 3 Sep 2015 11:57:14 -0400 Received: from mx2.suse.de ([195.135.220.15]:60049 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933299AbbICPqq (ORCPT ); Thu, 3 Sep 2015 11:46:46 -0400 Subject: Re: [Xen-devel] [PATCH] xen/p2m: fix extra memory regions accounting To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , David Vrabel , linux-kernel@vger.kernel.org References: <1441281916-38284-1-git-send-email-roger.pau@citrix.com> <55E83C46.8010701@suse.com> <55E85B61.4070203@citrix.com> <55E85CF3.40705@citrix.com> <55E85EB6.7060307@citrix.com> <55E85F52.9030708@suse.com> <55E860D5.5050609@citrix.com> <55E8654A.8020302@suse.com> <55E869A3.6030008@citrix.com> Cc: xen-devel@lists.xenproject.org, Boris Ostrovsky From: Juergen Gross Message-ID: <55E86B63.8020901@suse.com> Date: Thu, 3 Sep 2015 17:46:43 +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: <55E869A3.6030008@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 05:39 PM, Roger Pau Monné wrote: > El 03/09/15 a les 17.20, Juergen Gross ha escrit: >> On 09/03/2015 05:01 PM, David Vrabel wrote: >>> On 03/09/15 15:55, Juergen Gross wrote: >>>> On 09/03/2015 04:52 PM, David Vrabel wrote: >>>>> On 03/09/15 15:45, David Vrabel wrote: >>>>>> On 03/09/15 15:38, 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). >>>>>> >>>>>> We expand the reserved (i.e., non-RAM) areas down so they're fully >>>>>> covered with whole pages when we depopulate and 1:1 map them, we >>>>>> should >>>>>> add extra memory regions that cover these same areas. >>>>> >>>>> Ignore this. This was nonsense. >>>>> >>>>> We expand the reserved (i.e., non-RAM) areas so they're fully covered >>>>> with whole pages when we depopulate and 1:1 map them, we should add the >>>>> extra memory such that it does not overlap with with expanded regions. >>>>> i.e., round up the start and round down the end (like Roger's patch >>>>> does). >>>> >>>> Nearly. Roger's patch rounds up start and rounds down the size. It might >>>> add non-RAM partial pages to xen_extra_mem. >>> >>> Yes. You're right. >> >> Hmm, thinking more about it, I'd prefer to change xen_extra_mem to use >> pfns instead of physical addresses. This would make things much more >> clear. >> >> Roger, do you want to do the patch or should I? > > I can certainly take care of it if you are busy, otherwise I leave it to > you since you have more expertise on it :). Okay, I can do it. Should be ready soon... Juergen