From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752053AbdKWH4V (ORCPT ); Thu, 23 Nov 2017 02:56:21 -0500 Received: from bastet.se.axis.com ([195.60.68.11]:43541 "EHLO bastet.se.axis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751621AbdKWH4U (ORCPT ); Thu, 23 Nov 2017 02:56:20 -0500 Date: Thu, 23 Nov 2017 08:56:17 +0100 From: Jesper Nilsson To: Nicolas Pitre Cc: Jesper Nilsson , Guenter Roeck , Tejun Heo , Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mikael Starvik , linux-cris-kernel@axis.com Subject: Re: mm/percpu.c: use smarter memory allocation for struct pcpu_alloc_info (crisv32 hang) Message-ID: <20171123075617.GE20542@axis.com> References: <62a3b680-6dde-d308-3da8-9c9a2789b114@roeck-us.net> <20171120185138.GB23789@roeck-us.net> <20171120211114.GA25984@roeck-us.net> <20171121014818.GA360@roeck-us.net> <20171122153453.GB20542@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 22, 2017 at 03:17:00PM -0500, Nicolas Pitre wrote: > On Wed, 22 Nov 2017, Jesper Nilsson wrote: > > > On Mon, Nov 20, 2017 at 10:50:46PM -0500, Nicolas Pitre wrote: > > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > > On Mon, Nov 20, 2017 at 07:28:21PM -0500, Nicolas Pitre wrote: > > > > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > > > > > > > > > bdata->node_min_pfn=60000 PFN_PHYS(bdata->node_min_pfn)=c0000000 start_off=536000 region=c0536000 > > > > > > > > > > If PFN_PHYS(bdata->node_min_pfn)=c0000000 and > > > > > region=c0536000 that means phys_to_virt() is a no-op. > > > > > > > > > No, it is |= 0x80000000 > > > > > > Then the bootmem registration looks very fishy. If you have: > > > > > > > I think the problem is the 0x60000 in bdata->node_min_pfn. It is shifted > > > > left by PFN_PHYS, making it 0xc0000000, which in my understanding is > > > > a virtual address. > > > > > > Exact. > > > > > > #define __pa(x) ((unsigned long)(x) & 0x7fffffff) > > > #define __va(x) ((void *)((unsigned long)(x) | 0x80000000)) > > > > > > With that, the only possible physical address range you may have is > > > 0x40000000 - 0x7fffffff, and it better start at 0x40000000. If that's > > > not where your RAM is then something is wrong. > > > > > > This is in fact a very bad idea to define __va() and __pa() using > > > bitwise operations as this hides mistakes like defining physical RAM > > > address at 0xc0000000. Instead, it should look like: > > > > > > #define __pa(x) ((unsigned long)(x) - 0x80000000) > > > #define __va(x) ((void *)((unsigned long)(x) + 0x80000000)) > > > > > > This way, bad physical RAM address definitions will be caught > > > immediately. > > > > > > > That doesn't seem to be easy to fix. It seems there is a mixup of physical > > > > and virtual addresses in the architecture. > > > > > > Well... I don't think there is much else to say other than this needs > > > fixing. > > > > The memory map for the ETRAX FS has the SDRAM mapped at both 0x40000000-0x7fffffff > > and 0xc0000000-0xffffffff, and the difference is cached and non-cached. > > That is actively (ab)used in the port, unfortunately, allthough I'm > > uncertain if this is the problem in this case. > > It certainly is a problem. If your cached RAM is physically mapped at > 0xc0000000 and you want it to be virtually mapped at 0xc0000000 then you > should have: > > #define __pa(x) ((unsigned long)(x)) > #define __va(x) ((void *)(x)) > > i.e. no translation. Sorry, it's the other way around, cached memory is at 0x40000000 and non-cached is at 0xc0000000, so the translation is right, even if as you pointed out earlier, it should be performed differently. > For non-cached RAM access, there are specific > interfaces for that. For example, you could have dma_alloc_coherent() > take advantage of the fact that memory with the top bit cleared becomes > uncached. But __pa() is the wrong interface for obtaining uncached > memory. > > Nicolas /^JN - Jesper Nilsson -- Jesper Nilsson -- jesper.nilsson@axis.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id 3E3136B0033 for ; Thu, 23 Nov 2017 02:56:21 -0500 (EST) Received: by mail-lf0-f72.google.com with SMTP id k66so1318521lfg.14 for ; Wed, 22 Nov 2017 23:56:21 -0800 (PST) Received: from bastet.se.axis.com (bastet.se.axis.com. [195.60.68.11]) by mx.google.com with ESMTPS id 10si1797816lji.365.2017.11.22.23.56.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Nov 2017 23:56:19 -0800 (PST) Date: Thu, 23 Nov 2017 08:56:17 +0100 From: Jesper Nilsson Subject: Re: mm/percpu.c: use smarter memory allocation for struct pcpu_alloc_info (crisv32 hang) Message-ID: <20171123075617.GE20542@axis.com> References: <62a3b680-6dde-d308-3da8-9c9a2789b114@roeck-us.net> <20171120185138.GB23789@roeck-us.net> <20171120211114.GA25984@roeck-us.net> <20171121014818.GA360@roeck-us.net> <20171122153453.GB20542@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Nicolas Pitre Cc: Jesper Nilsson , Guenter Roeck , Tejun Heo , Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mikael Starvik , linux-cris-kernel@axis.com On Wed, Nov 22, 2017 at 03:17:00PM -0500, Nicolas Pitre wrote: > On Wed, 22 Nov 2017, Jesper Nilsson wrote: > > > On Mon, Nov 20, 2017 at 10:50:46PM -0500, Nicolas Pitre wrote: > > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > > On Mon, Nov 20, 2017 at 07:28:21PM -0500, Nicolas Pitre wrote: > > > > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > > > > > > > > > bdata->node_min_pfn=60000 PFN_PHYS(bdata->node_min_pfn)=c0000000 start_off=536000 region=c0536000 > > > > > > > > > > If PFN_PHYS(bdata->node_min_pfn)=c0000000 and > > > > > region=c0536000 that means phys_to_virt() is a no-op. > > > > > > > > > No, it is |= 0x80000000 > > > > > > Then the bootmem registration looks very fishy. If you have: > > > > > > > I think the problem is the 0x60000 in bdata->node_min_pfn. It is shifted > > > > left by PFN_PHYS, making it 0xc0000000, which in my understanding is > > > > a virtual address. > > > > > > Exact. > > > > > > #define __pa(x) ((unsigned long)(x) & 0x7fffffff) > > > #define __va(x) ((void *)((unsigned long)(x) | 0x80000000)) > > > > > > With that, the only possible physical address range you may have is > > > 0x40000000 - 0x7fffffff, and it better start at 0x40000000. If that's > > > not where your RAM is then something is wrong. > > > > > > This is in fact a very bad idea to define __va() and __pa() using > > > bitwise operations as this hides mistakes like defining physical RAM > > > address at 0xc0000000. Instead, it should look like: > > > > > > #define __pa(x) ((unsigned long)(x) - 0x80000000) > > > #define __va(x) ((void *)((unsigned long)(x) + 0x80000000)) > > > > > > This way, bad physical RAM address definitions will be caught > > > immediately. > > > > > > > That doesn't seem to be easy to fix. It seems there is a mixup of physical > > > > and virtual addresses in the architecture. > > > > > > Well... I don't think there is much else to say other than this needs > > > fixing. > > > > The memory map for the ETRAX FS has the SDRAM mapped at both 0x40000000-0x7fffffff > > and 0xc0000000-0xffffffff, and the difference is cached and non-cached. > > That is actively (ab)used in the port, unfortunately, allthough I'm > > uncertain if this is the problem in this case. > > It certainly is a problem. If your cached RAM is physically mapped at > 0xc0000000 and you want it to be virtually mapped at 0xc0000000 then you > should have: > > #define __pa(x) ((unsigned long)(x)) > #define __va(x) ((void *)(x)) > > i.e. no translation. Sorry, it's the other way around, cached memory is at 0x40000000 and non-cached is at 0xc0000000, so the translation is right, even if as you pointed out earlier, it should be performed differently. > For non-cached RAM access, there are specific > interfaces for that. For example, you could have dma_alloc_coherent() > take advantage of the fact that memory with the top bit cleared becomes > uncached. But __pa() is the wrong interface for obtaining uncached > memory. > > Nicolas /^JN - Jesper Nilsson -- Jesper Nilsson -- jesper.nilsson@axis.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org