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[2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by mx.google.com with ESMTPS id b10si22860314wrh.126.2019.07.25.14.58.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jul 2019 14:58:29 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux+linux-mm=kvack.org@armlinux.org.uk designates 2001:4d48:ad52:3201:214:fdff:fe10:1be6 as permitted sender) client-ip=2001:4d48:ad52:3201:214:fdff:fe10:1be6; Authentication-Results: mx.google.com; dkim=pass (test mode) header.i=@armlinux.org.uk header.s=pandora-2019 header.b=sHapK5Dv; spf=pass (google.com: best guess record for domain of linux+linux-mm=kvack.org@armlinux.org.uk designates 2001:4d48:ad52:3201:214:fdff:fe10:1be6 as permitted sender) smtp.mailfrom="linux+linux-mm=kvack.org@armlinux.org.uk"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3G0DbANSEEz3gBLVg4LbmF0CvfiTNd4gqwl2oAi+YHw=; b=sHapK5Dv01/JCHeQu/SjqvySW pH6NXKfPa0ocMNU8dGO4QMKJt+V/hxIZBWxflM6ndEmDYOb+0THMyDtpoiwsq1QwIEczr5gydc+AX ukWeOWFYxCs1H6b9ICoaEjcsxGhK/oWcWJZ2XRa7t1VukD9tmGNPRuMHBe/ljDRZlPMihyMqVlK2D Zix8A5XlQ9FwZM/jPoOI9e2CCXMdN+i0KM+peI6omltOm/LQWwmL8ST1sdCM4dZxZpjZ50MpqviaZ xvkaCb3IbY8GQo0+w56JWRDQeiSn6vs2kO1h0XtKVS+EnAzq8fGF8RKxA0nrZQogQb0j3TfenlS3k s2G1lrXVA==; 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 Cc: Anshuman Khandual , Mark Rutland , Kees Cook , Sri Krishna chowdary , Ard Biesheuvel , Masahiro Yamada , Tetsuo Handa , x86@kernel.org, Dave Hansen , linux-kernel@vger.kernel.org, Steven Price , linux-mm@kvack.org, Mark Brown , Andrew Morton , Michal Hocko , linux-arm-kernel@lists.infradead.org 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190725214222.GG30641@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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