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Tue, 24 Nov 2020 09:04:57 +0000 MIME-Version: 1.0 Date: Tue, 24 Nov 2020 09:04:57 +0000 From: Marc Zyngier To: Jianyong Wu 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 Cc: Justin He , kvm@vger.kernel.org, netdev@vger.kernel.org, richardcochran@gmail.com, linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com, Steven Price , Andre Przywara , john.stultz@linaro.org, yangbo.lu@nxp.com, pbonzini@redhat.com, tglx@linutronix.de, nd , will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm