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=-11.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 2D5E6C433DF for ; Wed, 12 Aug 2020 13:32:02 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 EBE75204FD for ; Wed, 12 Aug 2020 13:32:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sG0GOD9s"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="sYB7dZLH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EBE75204FD 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+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=merlin.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=JsTsFqW/NTOVUWaqLq/vNmdyvr/8bQWWOsWdYOW3sco=; b=sG0GOD9sd7cta7OBLWG00aGai iPzJPXfg6bHdo/0DcX6mLjRXHKP3IpCeaScQHMkEumdv9b/32uxgGHMi9w7hzWPjyV2vS4v2JUwvz ZDMu5Qh1iijy2937LiE5iHnlGa/CcluQY8prmo9P0g2on/YbNCwfm7X4AYkquN4uanf+mYWR50I9Y u0p0hVA9Xvh+5v41GnTpuQnB2DyN/sfDQIBiW86Hn+qqTIcQ/FHoRfsDN8ErzTJe+bxqpO0vDHjTx tZUVPleRoXPnje5VNqVmtw01mAN0rh7UKYDsN14C5xAoWVsoOwelogbu/0QffHRFu4jgpsRYjUtFW EBWymYe/Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k5qqC-0004A0-Sd; Wed, 12 Aug 2020 13:30:52 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k5qq8-00048K-UJ for linux-arm-kernel@lists.infradead.org; Wed, 12 Aug 2020 13:30:49 +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 3BAC8207F7; Wed, 12 Aug 2020 13:30:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597239048; bh=qONd+uebxuHxqWaUJyHKSu5dged4G+IxGWG78tjLPcM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sYB7dZLHVZ6TZh/+w9McXu9gV8/m4bTlrJ/NIEwTCZW44NkpnA/167w84fBx/RVUX ZXN7VctIATKR+floFs+XHZlRAUN0eNW/3EQi8WTVB7h+6jrGMMip+aqXsPMUYJwcI2 vW10Q56VWGZ2NWGM7Cw1D00tu9jMf0gseOQP1uZ8= Date: Wed, 12 Aug 2020 14:30:44 +0100 From: Will Deacon To: Gaurav Kohli Subject: Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system Message-ID: <20200812133043.GA8924@willie-the-truck> References: <1596550484-11029-1-git-send-email-gkohli@codeaurora.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1596550484-11029-1-git-send-email-gkohli@codeaurora.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-20200812_093049_096761_2C321ABA X-CRM114-Status: GOOD ( 16.09 ) 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: maz@kernel.org, neeraju@codeaurora.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org 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, Aug 04, 2020 at 07:44:42PM +0530, Gaurav Kohli wrote: > In a system where no cpu's implement SSBS, for > them no need to set pstate. This might help to save > few cpu cycles during context switch. > > Signed-off-by: Gaurav Kohli > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 6089638..79f80f1 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next) > struct pt_regs *regs = task_pt_regs(next); > > /* > + * For Targets which don't have SSBS support, they > + * can return from here. > + */ > + if (!IS_ENABLED(CONFIG_ARM64_SSBD)) > + return; Does this actually make a measurable difference? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel