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=-9.0 required=3.0 tests=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,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 54CABC43460 for ; Tue, 11 May 2021 09:13:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 286D161928 for ; Tue, 11 May 2021 09:13:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231325AbhEKJOM (ORCPT ); Tue, 11 May 2021 05:14:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:36270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231318AbhEKJOM (ORCPT ); Tue, 11 May 2021 05:14:12 -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 D04616157F; Tue, 11 May 2021 09:13:05 +0000 (UTC) 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 4.94.2) (envelope-from ) id 1lgORr-000doA-Os; Tue, 11 May 2021 10:13:03 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 11 May 2021 10:13:03 +0100 From: Marc Zyngier To: Geert Uytterhoeven Cc: jianyong.wu@arm.com, netdev , Yangbo Lu , John Stultz , Thomas Gleixner , Paolo Bonzini , seanjc@google.com, Richard Cochran , Mark Rutland , Will Deacon , Suzuki K Poulose , Andre Przywara , Steven Price , Lorenzo Pieralisi , Sudeep Holla , Linux Kernel Mailing List , Linux ARM , kvmarm@lists.cs.columbia.edu, KVM list , Steve Capper , justin.he@arm.com, Android Kernel Team Subject: Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 In-Reply-To: References: <20210330145430.996981-1-maz@kernel.org> <20210330145430.996981-8-maz@kernel.org> User-Agent: Roundcube Webmail/1.4.11 Message-ID: <6c522f8116f54fa6f23a2d217d966c5a@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: geert@linux-m68k.org, jianyong.wu@arm.com, netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, seanjc@google.com, richardcochran@gmail.com, Mark.Rutland@arm.com, will@kernel.org, suzuki.poulose@arm.com, Andre.Przywara@arm.com, steven.price@arm.com, lorenzo.pieralisi@arm.com, sudeep.holla@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, kernel-team@android.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 Hi Geert, On 2021-05-11 10:07, Geert Uytterhoeven wrote: > Hi Marc, Jianyong, > > On Tue, Mar 30, 2021 at 4:56 PM Marc Zyngier wrote: >> From: Jianyong Wu >> >> Currently, there is no mechanism to keep time sync between guest and >> host >> in arm/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 environment, we >> ask >> for higher time precision. >> >> kvm ptp clock, which chooses the host clock source as a reference >> clock to sync time between guest and host, has been adopted by x86 >> which takes the time sync order from milliseconds to nanoseconds. >> >> This patch enables kvm ptp clock for arm/arm64 and improves clock sync >> precision >> significantly. > >> --- a/drivers/ptp/Kconfig >> +++ b/drivers/ptp/Kconfig >> @@ -108,7 +108,7 @@ 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) || (HAVE_ARM_SMCCC_DISCOVERY && >> ARM_ARCH_TIMER) > > Why does this not depend on KVM_GUEST on ARM? > I.e. shouldn't the dependency be: > > KVM_GUEST && (X86 || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)) > > ? arm/arm64 do not select KVM_GUEST. Any kernel can be used for a guest, and KVM/arm64 doesn't know about this configuration symbol. Thanks, M. -- Jazz is not dead. It just smells funny...