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Date: Wed, 22 Jan 2014 11:38:55 +0000 From: Will Deacon <will.deacon@....com> To: Wang Nan <wangnan0@...wei.com> Cc: "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>, "stable@...r.kernel.org" <stable@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Geng Hui <hui.geng@...wei.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Eric Biederman <ebiederm@...ssion.com>, Russell King <rmk+kernel@....linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH 1/3] ARM: Premit ioremap() to map reserved pages 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 <wangnan0@...wei.com> > Cc: <stable@...r.kernel.org> # 3.4+ > Cc: Eric Biederman <ebiederm@...ssion.com> > Cc: Russell King <rmk+kernel@....linux.org.uk> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: Geng Hui <hui.geng@...wei.com> > --- > 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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