From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtB1sbozm109qNQYwRv73bmFkVmOGqwCC5kv0FQWhGf2/QhQwm0LO1FMLIZn2Xcx1jaNnrd ARC-Seal: i=1; a=rsa-sha256; t=1521379321; cv=none; d=google.com; s=arc-20160816; b=Ieapyak1gqG2KpIKO/Tyn3PvsaW+Y3vObDlBxtZW3vNKHcz6poBHELE6rv1rqQ5DDp EWFWIMWdoV+BAdc8ZfIiJht2Gp3o+LJLw895ahCwMmgBwI/N6Ku197ajSvKPIvN/9R/Z iIbnvNrKsPna5xH9Ud0qhNehzHU9+RZHhw65vHClZCmKXUPjuilOnlfRTx9LqFMdqoFi hgxppQlrvJ/1WZiWzad+pkAifJFhiJr+k7fhj4tJVdKNCPmLfUSjqeRSVBH9hsmaFgSn DEeKF9/dkrYI/eQ4LL7LfzQt9RHXgM96cG3JQdxuBD49I7Ekfg/ddJ9HkhYfdykJ891A iAlg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:user-agent:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date:dkim-signature :arc-authentication-results; bh=Mu+zw0sEoDNXoa54KZT6AUaZ2N+izpSA0EHE2l/KYu4=; b=n497eTXtkysY4fvFCRIfTTVm0odpe5qih7rIpzK9ZO7wrDDvGtc63KDK/QewGyy9eC DLU0MUv1woBSRGhLiO0SScrWrkt230j/N9p/1KFAaqfHmXe1O/tBz44+pFQuH9aTGiJs eymWlEtqs/SKhhCkCN8QWDoSNQZh2GJcClzIRO5BjYVUGbSmHrvRipAaLp6RgnaPH4Si M7rXVaqyWjahA44uJnf7bIEQcpK8AUA4CaggUL4aVwll6PNNPVOrSM4t570UNRSaNiaD o1Z85Icf3FP+L/zXlxT289x30HsZTBAUryPESa/YUQuyjMGNoC3q8O+RXnfoDxEJ+0ZL y2lA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@armlinux.org.uk header.s=pandora-2014 header.b=TjqD6kJu; spf=pass (google.com: best guess record for domain of linux+gregkh=linuxfoundation.org@armlinux.org.uk designates 2001:4d48:ad52:3201:214:fdff:fe10:1be6 as permitted sender) smtp.mailfrom=linux+gregkh=linuxfoundation.org@armlinux.org.uk; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk Authentication-Results: mx.google.com; dkim=pass header.i=@armlinux.org.uk header.s=pandora-2014 header.b=TjqD6kJu; spf=pass (google.com: best guess record for domain of linux+gregkh=linuxfoundation.org@armlinux.org.uk designates 2001:4d48:ad52:3201:214:fdff:fe10:1be6 as permitted sender) smtp.mailfrom=linux+gregkh=linuxfoundation.org@armlinux.org.uk; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk Date: Sun, 18 Mar 2018 13:21:27 +0000 From: Russell King - ARM Linux To: Abbott Liu Cc: aryabinin@virtuozzo.com, marc.zyngier@arm.com, kstewart@linuxfoundation.org, gregkh@linuxfoundation.org, f.fainelli@gmail.com, akpm@linux-foundation.org, afzal.mohd.ma@gmail.com, alexander.levin@verizon.com, glider@google.com, dvyukov@google.com, christoffer.dall@linaro.org, linux@rasmusvillemoes.dk, mawilcox@microsoft.com, pombredanne@nexb.com, ard.biesheuvel@linaro.org, vladimir.murzin@arm.com, nicolas.pitre@linaro.org, tglx@linutronix.de, thgarnie@google.com, dhowells@redhat.com, keescook@chromium.org, arnd@arndb.de, geert@linux-m68k.org, tixy@linaro.org, mark.rutland@arm.com, james.morse@arm.com, zhichao.huang@linaro.org, jinb.park7@gmail.com, labbott@redhat.com, philip@cog.systems, grygorii.strashko@linaro.org, catalin.marinas@arm.com, opendmb@gmail.com, kirill.shutemov@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org Subject: Re: [PATCH 1/7] 2 1-byte checks more safer for memory_is_poisoned_16 Message-ID: <20180318132126.GA565@n2100.armlinux.org.uk> References: <20180318125342.4278-1-liuwenliang@huawei.com> <20180318125342.4278-2-liuwenliang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180318125342.4278-2-liuwenliang@huawei.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: Russell King - ARM Linux X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595281327885358177?= X-GMAIL-MSGID: =?utf-8?q?1595281842279236623?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sun, Mar 18, 2018 at 08:53:36PM +0800, Abbott Liu wrote: > Because in some architecture(eg. arm) instruction set, non-aligned > access support is not very well, so 2 1-byte checks is more > safer than 1 2-byte check. The impact on performance is small > because 16-byte accesses are not too common. This is unnecessary: 1. a load of a 16-bit quantity will work as desired on modern ARMs. 2. Networking already relies on unaligned loads to work as per x86 (iow, an unaligned 32-bit load loads the 32-bits at the address even if it's not naturally aligned, and that also goes for 16-bit accesses.) If these are rare (which you say above - "not too common") then it's much better to leave the code as-is, because it will most likely be faster on modern CPUs, and the impact for older generation CPUs is likely to be low. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up