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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 1F682C64E7A for ; Tue, 24 Nov 2020 09:05:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3DEC20857 for ; Tue, 24 Nov 2020 09:05:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="VXXFrd6s" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731078AbgKXJFE (ORCPT ); Tue, 24 Nov 2020 04:05:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:60952 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731020AbgKXJFA (ORCPT ); Tue, 24 Nov 2020 04:05:00 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (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 B27A82075A; Tue, 24 Nov 2020 09:04:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606208699; bh=4dd2MKJS6YNqUDm2WfT0Eu4BA+fK0d9nlPFSmVAq7GY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=VXXFrd6sYgV0FGjunKo/ajZ40yGekO24Gi7WxGW9SzG9TnexvSCBR/WMuglY2+msF MMltO5oe/o8yrwATRTrpb6cskzP2RWV9wFzKZAjVD1peSe7W/gW3iTjgb4bTVqmUNR YmMs8gsuNfPW+1Ktf/0rTBtKM2RXdF8dhvsQn3zM= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1khUFt-00DC9a-CY; Tue, 24 Nov 2020 09:04:57 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 24 Nov 2020 09:04:57 +0000 From: Marc Zyngier To: Jianyong Wu Cc: netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, sean.j.christopherson@intel.com, richardcochran@gmail.com, Mark Rutland , will@kernel.org, Suzuki Poulose , Andre Przywara , Steven Price , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Steve Capper , Justin He , nd Subject: Re: [PATCH v15 7/9] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 In-Reply-To: References: <20201111062211.33144-1-jianyong.wu@arm.com> <20201111062211.33144-8-jianyong.wu@arm.com> <7bd3a66253ca4b7adbe2294eb598a23f@kernel.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <5dc5480d125ace6566ae616206c3ce3f@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: Jianyong.Wu@arm.com, netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, sean.j.christopherson@intel.com, richardcochran@gmail.com, Mark.Rutland@arm.com, will@kernel.org, Suzuki.Poulose@arm.com, Andre.Przywara@arm.com, Steven.Price@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Steve.Capper@arm.com, Justin.He@arm.com, nd@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Jianyong, On 2020-11-24 05:37, Jianyong Wu wrote: > Hi Marc, [...] >> > + >> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU >> NC_ID, >> > + ARM_PTP_NONE_COUNTER, &hvc_res); >> >> I really don't see the need to use a non-architectural counter ID. >> Using the virtual counter ID should just be fine, and shouldn't lead >> to any >> issue. >> > >> Am I missing something? > > In this function, no counter data is needed. If virtual counter ID is > used here, user may be confused with why we get virtual counter > data and do nothing with it. So I explicitly add a new "NONE" counter > ID to make it clear. > > WDYT? ITIABI (I Think It's A Bad Idea). There are two counters, and the API allows to retrieve the data for any of these two. If the "user" doesn't want to do anything with the data, that's their problem. Here, you can just sue the virtual counter, and that will give you the exact same semantic, without inventing non-architectural state. Thanks, M. -- Jazz is not dead. It just smells funny...