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Sun, 06 Sep 2020 11:00:39 +0100 Date: Sun, 06 Sep 2020 11:00:37 +0100 Message-ID: <87363vmdh6.wl-maz@kernel.org> From: Marc Zyngier To: Jianyong Wu Subject: Re: [PATCH v14 08/10] ptp: arm64: Enable ptp_kvm for arm64 In-Reply-To: <874kocmqqx.wl-maz@kernel.org> References: <20200904092744.167655-1-jianyong.wu@arm.com> <20200904092744.167655-9-jianyong.wu@arm.com> <874kocmqqx.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26.3 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 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, 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200906_060046_686964_6D9B54FB X-CRM114-Status: GOOD ( 17.41 ) 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: Mark.Rutland@arm.com, justin.he@arm.com, kvm@vger.kernel.org, suzuki.poulose@arm.com, netdev@vger.kernel.org, richardcochran@gmail.com, Steve.Capper@arm.com, linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com, steven.price@arm.com, john.stultz@linaro.org, yangbo.lu@nxp.com, pbonzini@redhat.com, tglx@linutronix.de, nd@arm.com, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.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 Sat, 05 Sep 2020 12:01:42 +0100, Marc Zyngier wrote: > > On Fri, 04 Sep 2020 10:27:42 +0100, > Jianyong Wu wrote: [...] > > +{ > > + ktime_t ktime; > > + > > + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID, > > + hvc_res); > > + if ((long long)(hvc_res->a0) < 0) > > + return -EOPNOTSUPP; > > Really? What if the cycle counter is a full 64 bit value, as it is > *mandated* on ARMv8.6? It means that the counter is now invalid for > half the lifetime of the system. Not acceptable either. Having re-read this, this field doesn't contain the cycle counter, but the time in ns. So checking for a negative value should actually be fine for quite a while. My other comments still stand though. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel