From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f182.google.com (mail-wi0-f182.google.com [209.85.212.182]) by kanga.kvack.org (Postfix) with ESMTP id 23E726B007B for ; Wed, 22 Jan 2014 08:28:09 -0500 (EST) Received: by mail-wi0-f182.google.com with SMTP id ex4so584419wid.15 for ; Wed, 22 Jan 2014 05:28:08 -0800 (PST) Received: from pandora.arm.linux.org.uk (pandora.arm.linux.org.uk. [2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by mx.google.com with ESMTPS id kj1si4995281wjc.162.2014.01.22.05.28.06 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 22 Jan 2014 05:28:06 -0800 (PST) Date: Wed, 22 Jan 2014 13:27:34 +0000 From: Russell King - ARM Linux Subject: Re: [PATCH 2/3] ARM: kexec: copying code to ioremapped area Message-ID: <20140122132734.GB15937@n2100.arm.linux.org.uk> References: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> <1390389916-8711-3-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1390389916-8711-3-git-send-email-wangnan0@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wang Nan 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, stable@vger.kernel.org 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. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- 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