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Wed, 12 Aug 2020 14:15:19 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id A1B15C433C6; Wed, 12 Aug 2020 14:15:18 +0000 (UTC) Received: from [192.168.1.4] (unknown [136.185.246.224]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: gkohli) by smtp.codeaurora.org (Postfix) with ESMTPSA id A72E6C433C9; Wed, 12 Aug 2020 14:15:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org A72E6C433C9 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=gkohli@codeaurora.org Subject: Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system To: Will Deacon References: <1596550484-11029-1-git-send-email-gkohli@codeaurora.org> <20200812133043.GA8924@willie-the-truck> From: Gaurav Kohli Message-ID: <5b1ad0e0-bbe7-9869-ee19-1b62023203ed@codeaurora.org> Date: Wed, 12 Aug 2020 19:45:12 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200812133043.GA8924@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200812_101552_309605_C14C673E X-CRM114-Status: GOOD ( 20.08 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 8/12/2020 7:00 PM, Will Deacon wrote: > 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 > Hi Will, While doing code review between older kernel and latest kernel for context switch case, there i have found this and thought it is good to have for non-ssbs system to return early(as this might improve). Please let me know if you want to run some tests. Regards Gaurav _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel