Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753054AbbKAUvN (ORCPT ); Sun, 1 Nov 2015 15:51:13 -0500 Received: from mail-wi0-f180.google.com ([209.85.212.180]:36131 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573AbbKAUvL (ORCPT ); Sun, 1 Nov 2015 15:51:11 -0500 MIME-Version: 1.0 In-Reply-To: <20151101203656.GR8644@n2100.arm.linux.org.uk> References: <1446409463.10982.4.camel@intel.com> <20151101203656.GR8644@n2100.arm.linux.org.uk> Date: Sun, 1 Nov 2015 12:51:09 -0800 Message-ID: Subject: Re: [GIT PULL] memremap fix for 4.3 (v2) From: Dan Williams To: Russell King - ARM Linux Cc: "torvalds@linux-foundation.org" , "akpm@linux-foundation.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "ard.biesheuvel@linaro.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2048 Lines: 53 On Sun, Nov 1, 2015 at 12:36 PM, Russell King - ARM Linux wrote: > 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; > Right, which means the caller is broken and shouldn't be using memremap, same as misuse of ioremap_cache today. -- 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/