From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34C5FC433E0 for ; Mon, 1 Jun 2020 07:03:20 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F1272207BC for ; Mon, 1 Jun 2020 07:03:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="rP5lmyja"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="mZqk14ig" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F1272207BC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tRgmdVMAr+Naen69YxdEoLoRmiPCgGv/hsGQFEZUc+o=; b=rP5lmyjaPNsQNH F9mQ4a8FOIpMYL5U/ZwYUnt34jci25xVRJGaymBHUz5IIx5SABxguJHV7KBG7hMen80wenVwoIjEw oQMFVl75zPfHOSPo/o1Kd3artXofOV1/Zz0wne49ZxkSI0IagtqwCxYXESypdHb5Kx6tonXlHgZn0 LbpdfWfrPE4itRaDEy7uhqMUi6jNEacLrECwNcHlCSyNmjmHBAhfS+OgeA3GpiGzYvI0JqMlQeuKe fNmOwx3RRlsMIVFiRzmZyEUBhdJzO6XEkBe7O7iKzgxq5f1U1LIcgey9Y0YX/ChnRDuhQkyM7+Bi5 Z8l0MPd+Nf75JBTfsMOA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jfeTf-0002S1-Me; Mon, 01 Jun 2020 07:03:19 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jfeTc-0002Rd-ON for linux-arm-kernel@lists.infradead.org; Mon, 01 Jun 2020 07:03:18 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 83EFC206E2; Mon, 1 Jun 2020 07:03:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590994996; bh=3NPQxs+C0cAbSGdr/kRkh+rf7Tn+bgfW4cso/Z6JYAA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mZqk14igi99/UvLo6UNwsvGYPEZZ9TYfPng3kTjh1CBKpNzc7AB+1QUtHAZ2CQ9nD VVC9eP5CxCDTm+kyXa02DaygjLdAObPQlVMq9dJEOCZJRHycu98ACtUfBNulzu67mj 48dpNX69dLlDeSra+WRvqSuT9gJaZmwjtT0xkgdY= Date: Mon, 1 Jun 2020 08:03:12 +0100 From: Will Deacon To: "Lixin (Victor, Kirin)" Subject: Re: Please help to confirm the risk if using TPIDRRO_EL0 to save CPU number, thanks. Message-ID: <20200601070311.GA8601@willie-the-truck> References: <1D289F1E6D91D2489524BBB0B8880A7DA1A39219@dggeml509-mbx.china.huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1D289F1E6D91D2489524BBB0B8880A7DA1A39219@dggeml509-mbx.china.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-20200601_000316_816938_7AF7798F X-CRM114-Status: UNSURE ( 9.27 ) X-CRM114-Notice: Please train this message. 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: "fujun \(F\)" , Wuxuecheng , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, May 29, 2020 at 09:03:37AM +0000, Lixin (Victor, Kirin) wrote: > Intel optimized getcpu syscall on Linux/Android system by using vDSO, = but > ARM doesn't do any optimizations for getcpu syscall. > = > In Apple open source, TPIDRRO_EL0/TPIDRURO is used to save the CPU num= ber, > [1]https://opensource.apple.com/source/xnu/xnu-4570.1.46/osfmk/arm/csw= itch.s.auto.html > = > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0Is there any risk if using TPIDRRO_EL= 0/TPIDRURO to implement > the vDSO for getcpu? Is there any possible to break any ARM ABI? Can y= ou > help us to confirm the considerations? Do you have a use-case for high-performance getcpu() that isn't better suited to rseq()? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel