From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752188AbdLAJts (ORCPT ); Fri, 1 Dec 2017 04:49:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46962 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894AbdLAJtp (ORCPT ); Fri, 1 Dec 2017 04:49:45 -0500 Date: Fri, 1 Dec 2017 17:49:39 +0800 From: Dave Young To: Michal Hocko Cc: linux-kernel@vger.kernel.org, pasha.tatashin@oracle.com, linux-mm@kvack.org, akpm@linux-foundation.org Subject: Re: [PATCH] mm: check pfn_valid first in zero_resv_unavail Message-ID: <20171201094939.GA3335@dhcp-128-65.nay.redhat.com> References: <20171130060431.GA2290@dhcp-128-65.nay.redhat.com> <20171130093521.3yxyq6xvo6zgaifc@dhcp22.suse.cz> <20171201085657.GA2291@dhcp-128-65.nay.redhat.com> <20171201091930.5ddygjl23owfovrz@dhcp22.suse.cz> <20171201092951.GA2943@dhcp-128-65.nay.redhat.com> <20171201094215.aenoqa5jepdc3jd5@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171201094215.aenoqa5jepdc3jd5@dhcp22.suse.cz> User-Agent: Mutt/1.9.1 (2017-09-22) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 01 Dec 2017 09:49:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/01/17 at 10:42am, Michal Hocko wrote: > On Fri 01-12-17 17:29:51, Dave Young wrote: > > On 12/01/17 at 10:19am, Michal Hocko wrote: > > > On Fri 01-12-17 16:56:57, Dave Young wrote: > > > > On 11/30/17 at 10:35am, Michal Hocko wrote: > > > [...] > > > > > Can we exclude that range from the memblock allocator instead? E.g. what > > > > > happens if somebody allocates from that range? > > > > > > > > It is a EFI BGRT image buffer provided by firmware, they are reserved > > > > always and can not be used to allocate memory. > > > > > > Hmm, I see but I was actually suggesting to remove this range from the > > > memblock allocator altogether (memblock_remove) as it shouldn't be there > > > in the first place. > > > > Oh, I'm not sure because it is introduced as a way for efi to reserve > > boot services areas to be persistent across kexec reboot. See > > drivers/firmware/efi/efi.c: efi_mem_reserve(), BGRT is only one user > > of it, there is esrt and maybe other users, I do not know if it is safe > > :( > > Hmm, so it this range ever backed by a valid pfn? I think it is in normal boot, just it does not appear in e820 across kdump reboot. For kdump kexec_tools provided e820 the last pfn only covers the kdump crashkernel ranges thus it is not mapped. > -- > Michal Hocko > SUSE Labs