From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Russell King (Oracle)" Date: Mon, 28 Feb 2022 10:57:18 +0000 Subject: Re: [PATCH V3 09/30] arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT Message-Id: List-Id: References: <1646045273-9343-1-git-send-email-anshuman.khandual@arm.com> <1646045273-9343-10-git-send-email-anshuman.khandual@arm.com> In-Reply-To: <1646045273-9343-10-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Anshuman Khandual Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, geert@linux-m68k.org, Christoph Hellwig , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linux-mips@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-s390@vger.kernel.org, linux-riscv@lists.infradead.org, linux-alpha@vger.kernel.org, linux-sh@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-parisc@vger.kernel.org, openrisc@lists.librecores.org, linux-um@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-arch@vger.kernel.org, Arnd Bergmann On Mon, Feb 28, 2022 at 04:17:32PM +0530, Anshuman Khandual wrote: > This defines and exports a platform specific custom vm_get_page_prot() via > subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX > macros can be dropped which are no longer needed. What I would really like to know is why having to run _code_ to work out what the page protections need to be is better than looking it up in a table. Not only is this more expensive in terms of CPU cycles, it also brings additional code size with it. I'm struggling to see what the benefit is. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!