From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Date: Wed, 22 Jan 2014 11:38:55 +0000 From: Will Deacon 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-Disposition: inline In-Reply-To: <1390389916-8711-2-git-send-email-wangnan0@huawei.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: Wang Nan Cc: "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "linux-mm@kvack.org" , Eric Biederman , Geng Hui , Russell King , Andrew Morton , "linux-arm-kernel@lists.infradead.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 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec