From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com [202.81.31.142]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qXMXh2jXLzDq6y for ; Sun, 27 Mar 2016 01:11:16 +1100 (AEDT) Received: from localhost by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 27 Mar 2016 00:11:15 +1000 Received: from d23relay06.au.ibm.com (d23relay06.au.ibm.com [9.185.63.219]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id B12243578052 for ; Sun, 27 Mar 2016 01:11:06 +1100 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u2QEAwUB21430296 for ; Sun, 27 Mar 2016 01:11:06 +1100 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u2QEAXgC009256 for ; Sun, 27 Mar 2016 01:10:34 +1100 Date: Sat, 26 Mar 2016 23:50:08 +1100 From: Gavin Shan To: Michael Ellerman Cc: Gavin Shan , linuxppc-dev@lists.ozlabs.org, zhlcindy@linux.vnet.ibm.com, bsingharora@gmail.com Subject: Re: [RFC] powerpc/mm: Support bootmem for PPC64 again Message-ID: <20160326125008.GA30131@gwshan> Reply-To: Gavin Shan References: <1458921821-14960-1-git-send-email-gwshan@linux.vnet.ibm.com> <3qXF961KWTz9s4x@ozlabs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <3qXF961KWTz9s4x@ozlabs.org> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, Mar 26, 2016 at 08:23:54PM +1100, Michael Ellerman wrote: >On Fri, 2016-25-03 at 16:03:41 UTC, Gavin Shan wrote: >> CONFIG_NO_BOOTMEM is enabled on PPC platforms by default. However, >> user might disable that to have bootmem for other purpose. So it's >> resonable to support it. > >Hi Gavin, > >Sorry but I don't understand. We deliberately removed bootmem support, and don't >want it back, it doesn't add anything other than complexity. See 10239733ee86 >("powerpc: Remove bootmem allocator"). > >I wasn't aware there was any way to enable it? If there is we should fix that. > [Cc Balbir so that I needn't reply separately] Michael, here's the history: Li, who is in the cc list, backports deferred page initialization feature from upstream kernel to RHEL 7.2 (3.10.0-357.el7, or RHEL7.3?). Eventually, she runs into system kernel crash that should be caused by memory corruption. In RHEL kernel, CONFIG_BOOTMEM and CONFIG_DEFERRED_STRUCT_PAGE_INIT are enabled at same time. Li observed the issue on pSeries platform. I jumped in to help understanding what was going on. I tried to reproduce the issue on PowerNV platform with upstream kernel (v4.5-rc7) and found bootmem is never supported. In order to trigger the system crash with exact scenario that Li had. I have to support bootmem first of all. I guess it's fine to remove bootmem which allocates memory in page granularity. From the perspective, it's not different from memblock. But user might still need bootmem supported in code level. The story I told might be not enough to get bootmem to be supported in code level. If that's the case, please ignore the patch. At least, we won't support bootmem in long term :-) Thanks, Gavin