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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:47974) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lGkrc-0004Jj-QB; Mon, 01 Mar 2021 15:53:40 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1lGkrb-0000Ux-Cr; Mon, 01 Mar 2021 15:53:39 +0000 Date: Mon, 1 Mar 2021 15:53:39 +0000 From: Russell King - ARM Linux admin To: Ard Biesheuvel Subject: Re: [PATCH v2 3/3] ARM: cache-v7: get rid of mini-stack Message-ID: <20210301155339.GW1463@shell.armlinux.org.uk> References: <20210210185532.8425-1-ardb@kernel.org> <20210210185532.8425-4-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210210185532.8425-4-ardb@kernel.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-20210301_105343_344489_EC99EA37 X-CRM114-Status: GOOD ( 15.13 ) 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: Marc Zyngier , Linus Walleij , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, Nicolas Pitre 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 Wed, Feb 10, 2021 at 07:55:32PM +0100, Ard Biesheuvel wrote: > Now that we have reduced the number of registers that we need to > preserve when calling v7_invalidate_l1 from the boot code, we can use > scratch registers to preserve the remaining ones, and get rid of the > mini stack entirely. This works around any issues regarding cache > behavior in relation to the uncached accesses to this memory, which is > hard to get right in the general case (i.e., both bare metal and under > virtualization) > > While at it, switch v7_invalidate_l1 to using ip as a scratch register > instead of r4. This makes the function AAPCS compliant, and removes the > need to stash r4 in ip across the call. You don't mention that we only do this for MP capable cores, which is in itself quite a big change - maybe that change should be a separate commit? -- 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