Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751872AbbBEWQH (ORCPT ); Thu, 5 Feb 2015 17:16:07 -0500 Received: from mail-ig0-f179.google.com ([209.85.213.179]:39139 "EHLO mail-ig0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751022AbbBEWQF (ORCPT ); Thu, 5 Feb 2015 17:16:05 -0500 MIME-Version: 1.0 In-Reply-To: <20150205174826.GD21970@e104818-lin.cambridge.arm.com> References: <1422881149-8177-3-git-send-email-hanjun.guo@linaro.org> <2422968.Es7R0p3loO@vostro.rjw.lan> <1422984576.18187.82.camel@deneb.redhat.com> <20150204112508.GB26006@e104818-lin.cambridge.arm.com> <1423066107.18187.99.camel@deneb.redhat.com> <20150204175734.GI26006@e104818-lin.cambridge.arm.com> <1423076294.18187.103.camel@deneb.redhat.com> <20150205104149.GA18158@e104818-lin.cambridge.arm.com> <1423144447.18187.110.camel@deneb.redhat.com> <54D39D6B.5090304@linaro.org> <20150205174826.GD21970@e104818-lin.cambridge.arm.com> Date: Thu, 5 Feb 2015 22:16:03 +0000 Message-ID: Subject: Re: [Linaro-acpi] [PATCH v8 02/21] acpi: fix acpi_os_ioremap for arm64 From: Ard Biesheuvel To: Catalin Marinas Cc: Al Stone , Mark Langsdorf , "linaro-acpi@lists.linaro.org" , Will Deacon , "wangyijing@huawei.com" , Rob Herring , Timur Tabi , Daniel Lezcano , "linux-acpi@vger.kernel.org" , "msalter@redhat.com" , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier , "jcm@redhat.com" , Mark Brown , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , Ashwin Chaugule , Randy Dunlap , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Olof Johansson 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: 2419 Lines: 46 On 5 February 2015 at 17:48, Catalin Marinas wrote: > On Thu, Feb 05, 2015 at 04:42:19PM +0000, Al Stone wrote: >> On 02/05/2015 06:54 AM, Mark Salter wrote: >> > On Thu, 2015-02-05 at 10:41 +0000, Catalin Marinas wrote: >> >> On Wed, Feb 04, 2015 at 06:58:14PM +0000, Mark Salter wrote: >> >>> On Wed, 2015-02-04 at 17:57 +0000, Catalin Marinas wrote: >> >>>> On Wed, Feb 04, 2015 at 04:08:27PM +0000, Mark Salter wrote: >> >>>>> acpi_os_remap() is used to map ACPI tables. These tables may be in ram >> >>>>> which are already included in the kernel's linear RAM mapping. So we >> >>>>> need ioremap_cache to avoid two mappings to the same physical page >> >>>>> having different caching attributes. >> >>>> >> >>>> What's the call path to acpi_os_ioremap() on such tables already in the >> >>>> linear mapping? I can see an acpi_map() function which already takes >> >>>> care of the RAM mapping case but there are other cases where >> >>>> acpi_os_ioremap() is called directly. For example, >> >>>> acpi_os_read_memory(), can it be called on both RAM and I/O? >> >>> >> >>> acpi_map() is the one I've seen. >> >> >> >> By default, if should_use_kmap() is not patched for arm64, it translates >> >> to page_is_ram(); acpi_map() would simply use a kmap() which returns the >> >> current kernel linear mapping on arm64. >> > >> > The problem with kmap() is that it only maps a single page. I've seen >> > tables over 4k which is why I patched acpi_map() not to use kmap() on >> > arm64. >> >> Right. Mark replied to this before I could; using kmap() enforced a 4k >> (one page) limit that we kept breaking with some ACPI tables being larger >> than that (DSDTs and SSDTs, fwiw). This would lead to some very odd behaviors >> when most but not all of a device definition was within the page; using the >> table checksums was one way of detecting the issues. > > OK. So I think Mark's original patch was ok, assuming that the System > Memory cases mentioned by Graeme are detected with page_is_ram(). > page_is_ram() returns whether a pfn is covered by the linear mapping, so memory before the kernel or after a mem= limit will be misidentified. -- 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/