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Tue, 11 May 2021 02:08:10 -0700 (PDT) MIME-Version: 1.0 References: <20210330145430.996981-1-maz@kernel.org> <20210330145430.996981-8-maz@kernel.org> In-Reply-To: <20210330145430.996981-8-maz@kernel.org> From: Geert Uytterhoeven Date: Tue, 11 May 2021 11:07:59 +0200 Message-ID: Subject: Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 To: Marc Zyngier , jianyong.wu@arm.com Cc: 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210511_020815_388671_0AA0C111 X-CRM114-Status: GOOD ( 25.73 ) /bin/ln: failed to access 'reaver_cache/texts/20210511_020815_388671_0AA0C111': No such file or directory X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210511_020815_388671_0AA0C111 X-CRM114-Status: GOOD ( 20.70 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 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)) ? > default y > help > This driver adds support for using kvm infrastructure as a PTP Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel