Messages in this thread | | | Date | Tue, 11 May 2021 10:13:03 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 |
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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 <maz@kernel.org> wrote: >> From: Jianyong Wu <jianyong.wu@arm.com> >> >> 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...
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