From mboxrd@z Thu Jan 1 00:00:00 1970 From: tixy@linaro.org (Jon Medhurst (Tixy)) Date: Mon, 10 Apr 2017 11:16:34 +0100 Subject: [PATCH v4] arm: Fix memory attribute inconsistencies when using fixmap In-Reply-To: <20170408165100.GA3589@afzalpc> References: <1491291087-17450-1-git-send-email-ard.biesheuvel@linaro.org> <20170405224245.GA17774@n2100.armlinux.org.uk> <1491486403.2950.3.camel@linaro.org> <1491494594.2950.7.camel@linaro.org> <20170408165100.GA3589@afzalpc> Message-ID: <1491819394.3172.1.camel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, 2017-04-08 at 22:21 +0530, afzal mohammed wrote: > Hi, > > On Thu, Apr 06, 2017 at 05:03:14PM +0100, Jon Medhurst (Tixy) wrote: > > To cope with the variety in ARM architectures and configurations, the > > pagetable attributes for kernel memory are generated at runtime to match > > the system the kernel finds itself on. This calculated value is stored > > in pgprot_kernel. > > > > However, when early fixmap support was added for ARM (commit > > a5f4c561b3b1) the attributes used for mappings were hard coded because > > pgprot_kernel is not set up early enough. Unfortunately, when fixmap is > > used after early boot this means the memory being mapped can have > > different attributes to existing mappings, potentially leading to > > unpredictable behaviour. A specific problem also exists due to the hard > > coded values not include the 'shareable' attribute which means on > > systems where this matters (e.g. those with multiple CPU clusters) the > > cache contents for a memory location can become inconsistent between > > CPUs. > > > > To resolve these issues we change fixmap to use the same memory > > attributes (from pgprot_kernel) that the rest of the kernel uses. To > > enable this we need to refactor the initialisation code so > > build_mem_type_table() is called early enough. Note, that relies on early > > param parsing for memory type overrides passed via the kernel command > > line, so we need to make sure this call is still after > > parse_early_params(). > > Tested-by: afzal mohammed > > with an emphasis on no-MMU's Thanks. I've now submitted this new version to the patch tracker... http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8667/3