From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f169.google.com (mail-pd0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id 357256B0035 for ; Wed, 22 Jan 2014 21:20:55 -0500 (EST) Received: by mail-pd0-f169.google.com with SMTP id v10so1176597pde.0 for ; Wed, 22 Jan 2014 18:20:54 -0800 (PST) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [119.145.14.64]) by mx.google.com with ESMTPS id s4si12047938pbg.93.2014.01.22.18.20.50 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 22 Jan 2014 18:20:53 -0800 (PST) Message-ID: <52E07B85.6030709@huawei.com> Date: Thu, 23 Jan 2014 10:16:37 +0800 From: Wang Nan MIME-Version: 1.0 Subject: Re: [PATCH 2/3] ARM: kexec: copying code to ioremapped area References: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> <1390389916-8711-3-git-send-email-wangnan0@huawei.com> <20140122132734.GB15937@n2100.arm.linux.org.uk> In-Reply-To: <20140122132734.GB15937@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux Cc: kexec@lists.infradead.org, Eric Biederman , Andrew Morton , Geng Hui , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 2014/1/22 21:27, Russell King - ARM Linux wrote: > On Wed, Jan 22, 2014 at 07:25:15PM +0800, Wang Nan wrote: >> ARM's kdump is actually corrupted (at least for omap4460), mainly because of >> cache problem: flush_icache_range can't reliably ensure the copied data >> correctly goes into RAM. > > Quite right too. You're mistake here is thinking that flush_icache_range() > should push it to RAM. That's incorrect. > > flush_icache_range() is there to deal with such things as loadable modules > and self modifying code, where the MMU is not being turned off. Hence, it > only flushes to the point of coherency between the I and D caches, and > any further levels of cache between that point and memory are not touched. > Why should it touch any more levels - it's not the function's purpose. > >> After mmu turned off and jump to the trampoline, kexec always failed due >> to random undef instructions. > > We already have code in the kernel which deals with shutting the MMU off. > An instance of how this can be done is illustrated in the soft_restart() > code path, and kexec already uses this. > > One of the first things soft_restart() does is turn off the outer cache - > which OMAP4 does have, but this can only be done if there is a single CPU > running. If there's multiple CPUs running, then the outer cache can't be > disabled, and that's the most likely cause of the problem you're seeing. > You are right, commit b25f3e1c (OMAP4/highbank: Flush L2 cache before disabling) solves my problem, it flushes outer cache before disabling. I have tested it in UP and SMP situations and it works (actually, omap4 has not ready to support kexec in SMP case, I insert an empty cpu_kill() to make it work), so the first 2 patches are unneeded. What about the 3rd one (ARM: allow kernel to be loaded in middle of phymem)? -- 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