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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:49922) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kVu4A-0003HE-Qn; Fri, 23 Oct 2020 11:12:58 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kVu4A-0008MK-4j; Fri, 23 Oct 2020 11:12:58 +0100 Date: Fri, 23 Oct 2020 11:12:58 +0100 From: Russell King - ARM Linux admin To: Miles Chen Subject: Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type Message-ID: <20201023101257.GZ1551@shell.armlinux.org.uk> References: <20201023091437.8225-1-miles.chen@mediatek.com> <20201023091437.8225-5-miles.chen@mediatek.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201023091437.8225-5-miles.chen@mediatek.com> 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-20201023_061301_289153_28B1B3DC X-CRM114-Status: GOOD ( 16.55 ) 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: wsd_upstream@mediatek.com, Catalin Marinas , linux-kernel@vger.kernel.org, Minchan Kim , linux-mediatek@lists.infradead.org, Suren Baghdasaryan , 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+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Oct 23, 2020 at 05:14:37PM +0800, Miles Chen wrote: > Since kernel no longer writes to the vector, try to replace > the vector mem type with read-only type and remove L_PTE_MT_VECTORS. > > from Catalin in [1]: > " > > I don't think this matters since the kernel no longer writes to the > > vectors page at run-time but it needs cleaning up a bit (and testing in > > case I missed something). IOW, do we still need a dedicated mapping type > > for the vectors or we can simply use the read-only user page attributes? > " Catalin is incorrect. If CONFIG_KUSER_HELPERS is enabled, then the vectors page is definitely written to - it's a user interface, so it's not going to change: #ifdef CONFIG_KUSER_HELPERS /* * User space must never try to access this * directly. Expect your app to break * eventually if you do so. The user helper * at 0xffff0fe0 must be used instead. (see * entry-armv.S for details) */ *((unsigned int *)0xffff0ff0) = val; #endif -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel