Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753035AbbKAUhP (ORCPT ); Sun, 1 Nov 2015 15:37:15 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:52820 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751615AbbKAUhM (ORCPT ); Sun, 1 Nov 2015 15:37:12 -0500 Date: Sun, 1 Nov 2015 20:36:56 +0000 From: Russell King - ARM Linux To: "Williams, Dan J" Cc: "torvalds@linux-foundation.org" , "akpm@linux-foundation.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "ard.biesheuvel@linaro.org" Subject: Re: [GIT PULL] memremap fix for 4.3 (v2) Message-ID: <20151101203656.GR8644@n2100.arm.linux.org.uk> References: <1446409463.10982.4.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1446409463.10982.4.camel@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1752 Lines: 51 On Sun, Nov 01, 2015 at 08:24:25PM +0000, Williams, Dan J wrote: > diff --git a/kernel/memremap.c b/kernel/memremap.c > index 72b0c66628b6..9d6b55587eaa 100644 > --- a/kernel/memremap.c > +++ b/kernel/memremap.c > @@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size) > } > #endif > > +static void *try_ram_remap(resource_size_t offset, size_t size) > +{ > + struct page *page = pfn_to_page(offset >> PAGE_SHIFT); > + > + /* In the simple case just return the existing linear address */ > + if (!PageHighMem(page)) > + return __va(offset); > + return NULL; /* fallback to ioremap_cache */ Right, so a highmem page results in this returning NULL, which will... > @@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags) > * the requested range is potentially in "System RAM" > */ > if (is_ram == REGION_INTERSECTS) > - addr = __va(offset); > - else > + addr = try_ram_remap(offset, size); > + if (!addr) > addr = ioremap_cache(offset, size); cause ioremap_cache() to be called. That falls through on ARM to: __arm_ioremap_pfn_caller() and we will hit this (as I've mentioned before through explanation rather than quoting code): /* * Don't allow RAM to be mapped - this causes problems with ARMv6+ */ if (WARN_ON(pfn_valid(pfn))) return NULL; -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- 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/