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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:37148) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1hqlkb-0002Yr-TM; Thu, 25 Jul 2019 22:58:14 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1hqlka-00062y-II; Thu, 25 Jul 2019 22:58:12 +0100 Date: Thu, 25 Jul 2019 22:58:12 +0100 From: Russell King - ARM Linux admin To: Matthew Wilcox Subject: Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers Message-ID: <20190725215812.GN1330@shell.armlinux.org.uk> References: <1564037723-26676-1-git-send-email-anshuman.khandual@arm.com> <1564037723-26676-2-git-send-email-anshuman.khandual@arm.com> <20190725143920.GW363@bombadil.infradead.org> <20190725213858.GK1330@shell.armlinux.org.uk> <20190725214222.GG30641@bombadil.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190725214222.GG30641@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_145833_817408_DFA26565 X-CRM114-Status: GOOD ( 15.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , x86@kernel.org, Kees Cook , Sri Krishna chowdary , Ard Biesheuvel , Tetsuo Handa , Anshuman Khandual , Dave Hansen , linux-kernel@vger.kernel.org, Steven Price , linux-mm@kvack.org, Masahiro Yamada , Mark Brown , Andrew Morton , Michal Hocko , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jul 25, 2019 at 02:42:22PM -0700, Matthew Wilcox wrote: > On Thu, Jul 25, 2019 at 10:38:58PM +0100, Russell King - ARM Linux admin wrote: > > On Thu, Jul 25, 2019 at 07:39:21AM -0700, Matthew Wilcox wrote: > > > But 'page' isn't necessarily PMD-aligned. I don't think we can rely on > > > architectures doing the right thing if asked to make a PMD for a randomly > > > aligned page. > > > > > > How about finding the physical address of something like kernel_init(), > > > and using the corresponding pte/pmd/pud/p4d/pgd that encompasses that > > > address? It's also better to pass in the pfn/page rather than using global > > > variables to communicate to the test functions. > > > > There are architectures (32-bit ARM) where the kernel is mapped using > > section mappings, and we don't expect the Linux page table walking to > > work for section mappings. > > This test doesn't go so far as to insert the PTE/PMD/PUD/... into the > page tables. It merely needs an appropriately aligned PFN to create a > PTE/PMD/PUD/... from. Well, in any case, c085ac68 t kernel_init so I'm not sure that would be an improvement. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel