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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:44866) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kuCbT-00053K-8j; Tue, 29 Dec 2020 10:51:47 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kuCbP-0001Ae-S2; Tue, 29 Dec 2020 10:51:43 +0000 Date: Tue, 29 Dec 2020 10:51:43 +0000 From: Russell King - ARM Linux admin To: "Leizhen (ThunderTown)" Subject: Re: [PATCH 1/1] ARM: LPAE: use phys_addr_t instead of unsigned long in outercache hooks Message-ID: <20201229105143.GL1551@shell.armlinux.org.uk> References: <20201225114458.1334-1-thunder.leizhen@huawei.com> <20201226121346.GB1551@shell.armlinux.org.uk> <3a597586-2bce-66cf-b9f8-4bb667a600d0@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <3a597586-2bce-66cf-b9f8-4bb667a600d0@huawei.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-20201229_055155_386720_DDD3FCCD X-CRM114-Status: GOOD ( 24.29 ) 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: Jason Cooper , Arnd Bergmann , Greg Kroah-Hartman , Will Deacon , linux-kernel , Haojian Zhuang , linux-arm-kernel 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 Tue, Dec 29, 2020 at 02:30:56PM +0800, Leizhen (ThunderTown) wrote: > > > On 2020/12/26 20:13, Russell King - ARM Linux admin wrote: > > On Fri, Dec 25, 2020 at 07:44:58PM +0800, Zhen Lei wrote: > >> The outercache of some Hisilicon SOCs support physical addresses wider > >> than 32-bits. The unsigned long datatype is not sufficient for mapping > >> physical addresses >= 4GB. The commit ad6b9c9d78b9 ("ARM: 6671/1: LPAE: > >> use phys_addr_t instead of unsigned long in outercache functions") has > >> already modified the outercache functions. But the parameters of the > >> outercache hooks are not changed. This patch use phys_addr_t instead of > >> unsigned long in outercache hooks: inv_range, clean_range, flush_range. > >> > >> To ensure the outercache that does not support LPAE works properly, do > >> cast phys_addr_t to unsigned long by adding a middle-tier function. > > > > Please don't do that. The cast can be done inside the L2 functions > > themselves without needing all these additional functions. > > OK. At first, I wanted to fit in like this: > > -static void l2c220_inv_range(unsigned long start, unsigned long end) > +static void l2c220_inv_range(phys_addr_t lpae_start, phys_addr_t lpae_end) > { > + unsigned long start = lpae_start; > + unsigned long end = lpae_end; It sounds like there should be a "but..." clause here. This is exactly what I'm suggesting you should be doing. Currently, there's a silent narrowing cast in every single caller of the outer_.*_range() functions and you're only moving it from the callsites to inside the called functions. > > We probably ought to also add some protection against addresses > 4GB, > > although these are hot paths, so we don't want to add tests in these > > functions. Maybe instead checking whether the system has memory above > > 4GB while the L2 cache is being initialised would be a good idea? > > I'm sorry, I didn't quite understand what you meant. Currently, the > biggest problem is the compilation problem. The sizeof(long) may be > 32, and the 64-bit physical address cannot be transferred from outcache > functions to outcache hooks. What I mean is that we really ought to warn if the L2C310 code tries to initialise on a system where memory is above 4GB. However, it's very unlikely that such a system exists, so it's probably fine not implement a check, but it just feels fragile to be truncating the 64-bit address to 32-bit on a kernel that _could_ support higher addresses, even though that's exactly what is happening today (kind of by accident - I don't think anyone realised.) -- 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