Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755348AbaAVLju (ORCPT ); Wed, 22 Jan 2014 06:39:50 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:52108 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753140AbaAVLjp (ORCPT ); Wed, 22 Jan 2014 06:39:45 -0500 Date: Wed, 22 Jan 2014 11:38:55 +0000 From: Will Deacon To: Wang Nan Cc: "kexec@lists.infradead.org" , "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Geng Hui , "linux-mm@kvack.org" , Eric Biederman , Russell King , Andrew Morton , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 1/3] ARM: Premit ioremap() to map reserved pages Message-ID: <20140122113855.GH1621@mudshark.cambridge.arm.com> References: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> <1390389916-8711-2-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1390389916-8711-2-git-send-email-wangnan0@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 22, 2014 at 11:25:14AM +0000, Wang Nan wrote: > This patch relaxes the restriction set by commit 309caa9cc, which > prohibit ioremap() on all kernel managed pages. > > Other architectures, such as x86 and (some specific platforms of) powerpc, > allow such mapping. > > ioremap() pages is an efficient way to avoid arm's mysterious cache control. > This feature will be used for arm kexec support to ensure copied data goes into > RAM even without cache flushing, because we found that flush_cache_xxx can't > reliably flush code to memory. > > Signed-off-by: Wang Nan > Cc: # 3.4+ > Cc: Eric Biederman > Cc: Russell King > Cc: Andrew Morton > Cc: Geng Hui > --- > arch/arm/mm/ioremap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c > index f123d6e..98b1c10 100644 > --- a/arch/arm/mm/ioremap.c > +++ b/arch/arm/mm/ioremap.c > @@ -298,7 +298,7 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn, > /* > * Don't allow RAM to be mapped - this causes problems with ARMv6+ > */ > - if (WARN_ON(pfn_valid(pfn))) > + if (WARN_ON(pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn)))) Since reserved pages can still be mapped, how does this avoid the cacheable alias issue fixed by 309caa9cc6ff ("ARM: Prohibit ioremap() on kernel managed RAM")? Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/