From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-yw1-xc43.google.com ([2607:f8b0:4864:20::c43]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gf81P-0000AB-R8 for kexec@lists.infradead.org; Thu, 03 Jan 2019 18:47:13 +0000 Received: by mail-yw1-xc43.google.com with SMTP id i73so13620960ywg.3 for ; Thu, 03 Jan 2019 10:47:11 -0800 (PST) Date: Thu, 3 Jan 2019 10:47:06 -0800 From: Tejun Heo Subject: Re: [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr Message-ID: <20190103184706.GU2509588@devbig004.ftw2.facebook.com> References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-2-git-send-email-kernelfans@gmail.com> <20181231084018.GA28478@rapoport-lnx> <20190102092749.GA22664@rapoport-lnx> <20190102101804.GD1990@MiWiFi-R3L-srv> <20190102170537.GA3591@rapoport-lnx> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190102170537.GA3591@rapoport-lnx> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Mike Rapoport Cc: Michal Hocko , kexec@lists.infradead.org, Stefan Agner , Tang Chen , linux-mm@kvack.org, Yaowei Bai , Baoquan He , Jonathan Corbet , Pavel Tatashin , linux-acpi@vger.kernel.org, Dave Young , Daniel Vacek , vgoyal@redhat.com, Len Brown , Nicholas Piggin , Mike Rapoport , Pingfan Liu , yinghai@kernel.org, Naoya Horiguchi , Mathieu Malaterre , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, Andrew Morton Hello, On Wed, Jan 02, 2019 at 07:05:38PM +0200, Mike Rapoport wrote: > I agree that currently the bottom-up allocation after the kernel text has > issues with KASLR. But this issues are not necessarily related to the > memory hotplug. Even with a single memory node, a bottom-up allocation will > fail if KASLR would put the kernel near the end of node0. > > What I am trying to understand is whether there is a fundamental reason to > prevent allocations from [0, kernel_start)? > > Maybe Tejun can recall why he suggested to start bottom-up allocations from > kernel_end. That's from 79442ed189ac ("mm/memblock.c: introduce bottom-up allocation mode"). I wasn't involved in that patch, so no idea why the restrictions were added, but FWIW it doesn't seem necessary to me. Thanks. -- tejun _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr Date: Thu, 3 Jan 2019 10:47:06 -0800 Message-ID: <20190103184706.GU2509588@devbig004.ftw2.facebook.com> References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-2-git-send-email-kernelfans@gmail.com> <20181231084018.GA28478@rapoport-lnx> <20190102092749.GA22664@rapoport-lnx> <20190102101804.GD1990@MiWiFi-R3L-srv> <20190102170537.GA3591@rapoport-lnx> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190102170537.GA3591@rapoport-lnx> Sender: linux-kernel-owner@vger.kernel.org To: Mike Rapoport Cc: Baoquan He , Pingfan Liu , linux-acpi@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org, Tang Chen , "Rafael J. Wysocki" , Len Brown , Andrew Morton , Mike Rapoport , Michal Hocko , Jonathan Corbet , Yaowei Bai , Pavel Tatashin , Nicholas Piggin , Naoya Horiguchi , Daniel Vacek , Mathieu Malaterre , Stefan Agner , Dave Young , yinghai@kernel.org, vgoyal@redhat.com, linux-kernel@vger.kernel.o List-Id: linux-acpi@vger.kernel.org Hello, On Wed, Jan 02, 2019 at 07:05:38PM +0200, Mike Rapoport wrote: > I agree that currently the bottom-up allocation after the kernel text has > issues with KASLR. But this issues are not necessarily related to the > memory hotplug. Even with a single memory node, a bottom-up allocation will > fail if KASLR would put the kernel near the end of node0. > > What I am trying to understand is whether there is a fundamental reason to > prevent allocations from [0, kernel_start)? > > Maybe Tejun can recall why he suggested to start bottom-up allocations from > kernel_end. That's from 79442ed189ac ("mm/memblock.c: introduce bottom-up allocation mode"). I wasn't involved in that patch, so no idea why the restrictions were added, but FWIW it doesn't seem necessary to me. Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw1-f70.google.com (mail-yw1-f70.google.com [209.85.161.70]) by kanga.kvack.org (Postfix) with ESMTP id AECD48E0002 for ; Thu, 3 Jan 2019 13:47:11 -0500 (EST) Received: by mail-yw1-f70.google.com with SMTP id p20so11128104ywe.5 for ; Thu, 03 Jan 2019 10:47:11 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 195sor7609305ywh.176.2019.01.03.10.47.10 for (Google Transport Security); Thu, 03 Jan 2019 10:47:10 -0800 (PST) Date: Thu, 3 Jan 2019 10:47:06 -0800 From: Tejun Heo Subject: Re: [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr Message-ID: <20190103184706.GU2509588@devbig004.ftw2.facebook.com> References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-2-git-send-email-kernelfans@gmail.com> <20181231084018.GA28478@rapoport-lnx> <20190102092749.GA22664@rapoport-lnx> <20190102101804.GD1990@MiWiFi-R3L-srv> <20190102170537.GA3591@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190102170537.GA3591@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Mike Rapoport Cc: Baoquan He , Pingfan Liu , linux-acpi@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org, Tang Chen , "Rafael J. Wysocki" , Len Brown , Andrew Morton , Mike Rapoport , Michal Hocko , Jonathan Corbet , Yaowei Bai , Pavel Tatashin , Nicholas Piggin , Naoya Horiguchi , Daniel Vacek , Mathieu Malaterre , Stefan Agner , Dave Young , yinghai@kernel.org, vgoyal@redhat.com, linux-kernel@vger.kernel.org Hello, On Wed, Jan 02, 2019 at 07:05:38PM +0200, Mike Rapoport wrote: > I agree that currently the bottom-up allocation after the kernel text has > issues with KASLR. But this issues are not necessarily related to the > memory hotplug. Even with a single memory node, a bottom-up allocation will > fail if KASLR would put the kernel near the end of node0. > > What I am trying to understand is whether there is a fundamental reason to > prevent allocations from [0, kernel_start)? > > Maybe Tejun can recall why he suggested to start bottom-up allocations from > kernel_end. That's from 79442ed189ac ("mm/memblock.c: introduce bottom-up allocation mode"). I wasn't involved in that patch, so no idea why the restrictions were added, but FWIW it doesn't seem necessary to me. Thanks. -- tejun