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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 3B4F1C433E2 for ; Sat, 5 Sep 2020 11:02:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E7C752074B for ; Sat, 5 Sep 2020 11:02:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599303734; bh=osTqwp5BpMzq89ho/FwzSAexu/TNdqbCeQ4p3g+kYzI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=yyPBYaX5tbJCOD1ePM5Nx7fKryc8j1vkxW0jfK1xmn1LhxTwJ3/zOiKukMA1ySpCS 1ICRf80J/iHCrQNNY1l35/ka5geK1Yg8CT6eInGywVbzmDoS/SmnoQpx+cL63CGdfw xMfzdSW8gx2gTqswMGgWJmmmDivq74pVVQPsZNM4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728469AbgIELB7 (ORCPT ); Sat, 5 Sep 2020 07:01:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:56576 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726597AbgIELBr (ORCPT ); Sat, 5 Sep 2020 07:01:47 -0400 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 96F592074B; Sat, 5 Sep 2020 11:01:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599303705; bh=osTqwp5BpMzq89ho/FwzSAexu/TNdqbCeQ4p3g+kYzI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qyWXGrxPdr5xSZKWo90rjBCbkMd6d2Wij1PuYwr+tjkY9KNxgIMTzaMmjTu92UM5m k6pm/f/tzmPc3micqB04z+mMdcRB5zq+BNZu5exoRkE03FNUY2h2WSECJCpCPBPpDO 6s1QPH8JE+9xV/h+I564UojboF1OeYvscQxqWTLc= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kEVx1-009M2u-M9; Sat, 05 Sep 2020 12:01:43 +0100 Date: Sat, 05 Sep 2020 12:01:42 +0100 Message-ID: <874kocmqqx.wl-maz@kernel.org> 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@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 Subject: Re: [PATCH v14 08/10] ptp: arm64: Enable ptp_kvm for arm64 In-Reply-To: <20200904092744.167655-9-jianyong.wu@arm.com> References: <20200904092744.167655-1-jianyong.wu@arm.com> <20200904092744.167655-9-jianyong.wu@arm.com> 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") Content-Type: text/plain; charset=US-ASCII 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 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 04 Sep 2020 10:27:42 +0100, Jianyong Wu wrote: > > Currently, there is no mechanism to keep time sync between guest and host > in arm64 virtualization environment. Time in guest will drift compared > with host after boot up as they may both use third party time sources > to correct their time respectively. The time deviation will be in order > of milliseconds. But in some scenarios,like in cloud envirenment, we ask > for higher time precision. > > kvm ptp clock, which choose the host clock source as a reference > clock to sync time between guest and host, has been adopted by x86 > which makes the time sync order from milliseconds to nanoseconds. > > This patch enables kvm ptp clock for arm64 and improve clock sync precison > significantly. > > Test result comparisons between with kvm ptp clock and without it in arm64 > are as follows. This test derived from the result of command 'chronyc > sources'. we should take more care of the last sample column which shows > the offset between the local clock and the source at the last measurement. > > no kvm ptp in guest: > MS Name/IP address Stratum Poll Reach LastRx Last sample > ======================================================================== > ^* dns1.synet.edu.cn 2 6 377 13 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 21 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 29 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 37 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 45 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 53 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 61 +1040us[+1581us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 4 -130us[ +796us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 12 -130us[ +796us] +/- 21ms > ^* dns1.synet.edu.cn 2 6 377 20 -130us[ +796us] +/- 21ms > > in host: > MS Name/IP address Stratum Poll Reach LastRx Last sample > ======================================================================== > ^* 120.25.115.20 2 7 377 72 -470us[ -603us] +/- 18ms > ^* 120.25.115.20 2 7 377 92 -470us[ -603us] +/- 18ms > ^* 120.25.115.20 2 7 377 112 -470us[ -603us] +/- 18ms > ^* 120.25.115.20 2 7 377 2 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 22 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 43 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 63 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 83 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 103 +872ns[-6808ns] +/- 17ms > ^* 120.25.115.20 2 7 377 123 +872ns[-6808ns] +/- 17ms > > The dns1.synet.edu.cn is the network reference clock for guest and > 120.25.115.20 is the network reference clock for host. we can't get the > clock error between guest and host directly, but a roughly estimated value > will be in order of hundreds of us to ms. > > with kvm ptp in guest: > chrony has been disabled in host to remove the disturb by network clock. > > MS Name/IP address Stratum Poll Reach LastRx Last sample > ======================================================================== > * PHC0 0 3 377 8 -7ns[ +1ns] +/- 3ns > * PHC0 0 3 377 8 +1ns[ +16ns] +/- 3ns > * PHC0 0 3 377 6 -4ns[ -0ns] +/- 6ns > * PHC0 0 3 377 6 -8ns[ -12ns] +/- 5ns > * PHC0 0 3 377 5 +2ns[ +4ns] +/- 4ns > * PHC0 0 3 377 13 +2ns[ +4ns] +/- 4ns > * PHC0 0 3 377 12 -4ns[ -6ns] +/- 4ns > * PHC0 0 3 377 11 -8ns[ -11ns] +/- 6ns > * PHC0 0 3 377 10 -14ns[ -20ns] +/- 4ns > * PHC0 0 3 377 8 +4ns[ +5ns] +/- 4ns > > The PHC0 is the ptp clock which choose the host clock as its source > clock. So we can see that the clock difference between host and guest > is in order of ns. > > Signed-off-by: Jianyong Wu > --- > drivers/clocksource/arm_arch_timer.c | 24 +++++++++++++ > drivers/ptp/Kconfig | 2 +- > drivers/ptp/ptp_kvm_arm64.c | 53 ++++++++++++++++++++++++++++ > 3 files changed, 78 insertions(+), 1 deletion(-) > create mode 100644 drivers/ptp/ptp_kvm_arm64.c > > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index d55acffb0b90..aaf286e90092 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -1650,3 +1650,27 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table) > } > TIMER_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init); > #endif > + > +#if IS_ENABLED(CONFIG_PTP_1588_CLOCK_KVM) > +#include > +int kvm_arch_ptp_get_crosststamp(unsigned long *cycle, struct timespec64 *ts, > + struct clocksource **cs) > +{ > + struct arm_smccc_res hvc_res; > + ktime_t ktime; > + > + /* Currently, linux guest will always use the virtual counter */ > + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID, > + ARM_PTP_VIRT_COUNTER, &hvc_res); > + if ((long long)(hvc_res.a0) < 0) > + return -EOPNOTSUPP; > + > + ktime = (long long)hvc_res.a0; > + *ts = ktime_to_timespec64(ktime); > + *cycle = (long long)hvc_res.a1; > + *cs = &clocksource_counter; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(kvm_arch_ptp_get_crosststamp); > +#endif > diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig > index 942f72d8151d..127e96f14f89 100644 > --- a/drivers/ptp/Kconfig > +++ b/drivers/ptp/Kconfig > @@ -106,7 +106,7 @@ config PTP_1588_CLOCK_PCH > config PTP_1588_CLOCK_KVM > tristate "KVM virtual PTP clock" > depends on PTP_1588_CLOCK > - depends on KVM_GUEST && X86 > + depends on KVM_GUEST && X86 || ARM64 && ARM_ARCH_TIMER && ARM_PSCI_FW > default y > help > This driver adds support for using kvm infrastructure as a PTP > diff --git a/drivers/ptp/ptp_kvm_arm64.c b/drivers/ptp/ptp_kvm_arm64.c > new file mode 100644 > index 000000000000..961abed93dfd > --- /dev/null > +++ b/drivers/ptp/ptp_kvm_arm64.c > @@ -0,0 +1,53 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Virtual PTP 1588 clock for use with KVM guests > + * Copyright (C) 2019 ARM Ltd. > + * All Rights Reserved > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +int kvm_arch_ptp_init(void) > +{ > + struct arm_smccc_res hvc_res; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID, > + &hvc_res); > + if (!(hvc_res.a0 | BIT(ARM_SMCCC_KVM_FUNC_KVM_PTP))) > + return -EOPNOTSUPP; > + > + return 0; What happens if the ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID function isn't implemented (on an old kernel or a non-KVM hypervisor)? The expected behaviour is that a0 will contain SMCCC_RET_NOT_SUPPORTED, which is -1. The result is that this function always returns "supported". Not an acceptable behaviour. > +} > + > +int kvm_arch_ptp_get_clock_generic(struct timespec64 *ts, > + struct arm_smccc_res *hvc_res) Why isn't this static? > +{ > + 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. > + > + ktime = (long long)hvc_res->a0; > + *ts = ktime_to_timespec64(ktime); > + > + return 0; > +} > + > +int kvm_arch_ptp_get_clock(struct timespec64 *ts) > +{ > + struct arm_smccc_res hvc_res; > + > + kvm_arch_ptp_get_clock_generic(ts, &hvc_res); > + > + return 0; > +} > -- > 2.17.1 > > It is now obvious that the API between kernel and hypervisor is pretty busted, and it goes beyond the 32bit support. I wish you paid more attention to this kind of detail. M. -- Without deviation from the norm, progress is not possible.