From: Marc Zyngier <maz@kernel.org>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: justin.he@arm.com, kvm@vger.kernel.org, netdev@vger.kernel.org,
richardcochran@gmail.com, linux-kernel@vger.kernel.org,
steven.price@arm.com, Andre.Przywara@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
Subject: Re: [PATCH v16 0/9] Enable ptp_kvm for arm/arm64
Date: Tue, 02 Feb 2021 14:15:15 +0000 [thread overview]
Message-ID: <74108ee1d0021acbdd7aed5b467e5432@kernel.org> (raw)
In-Reply-To: <20201209060932.212364-1-jianyong.wu@arm.com>
On 2020-12-09 06:09, Jianyong Wu wrote:
> Currently, we offen use ntp (sync time with remote network clock)
> to sync time in VM. But the precision of ntp is subject to network
> delay
> so it's difficult to sync time in a high precision.
>
> kvm virtual ptp clock (ptp_kvm) offers another way to sync time in VM,
> as the remote clock locates in the host instead of remote network
> clock.
> It targets to sync time between guest and host in virtualization
> environment and in this way, we can keep the time of all the VMs
> running
> in the same host in sync. In general, the delay of communication
> between
> host and guest is quiet small, so ptp_kvm can offer time sync precision
> up to in order of nanosecond. Please keep in mind that ptp_kvm just
> limits itself to be a channel which transmit the remote clock from
> host to guest and leaves the time sync jobs to an application, eg.
> chrony,
> in usersapce in VM.
>
> How ptp_kvm works:
> After ptp_kvm initialized, there will be a new device node under
> /dev called ptp%d. A guest userspace service, like chrony, can use this
> device to get host walltime, sometimes also counter cycle, which
> depends
> on the service it calls. Then this guest userspace service can use
> those
> data to do the time sync for guest.
> here is a rough sketch to show how kvm ptp clock works.
>
> |----------------------------|
> |--------------------------|
> | guest userspace | | host
> |
> |ioctl -> /dev/ptp%d | |
> |
> | ^ | | |
> |
> |----------------------------| |
> |
> | | | guest kernel | |
> |
> | | V (get host walltime/counter cycle)
> |
> | ptp_kvm -> hypercall - - - - - - - - - - ->hypercall service
> |
> | <- - - - - - - - - - - -
> |
> |----------------------------|
> |--------------------------|
>
> 1. time sync service in guest userspace call ptp device through
> /dev/ptp%d.
> 2. ptp_kvm module in guest receives this request then invoke hypercall
> to route
> into host kernel to request host walltime/counter cycle.
> 3. ptp_kvm hypercall service in host response to the request and send
> data back.
> 4. ptp (not ptp_kvm) in guest copy the data to userspace.
>
> This ptp_kvm implementation focuses itself to step 2 and 3 and step 2
> works
> in guest comparing step 3 works in host kernel.
FWIW, and in order to speed up the review, I've posted a reworked
version[0] of this series with changes that address the comments
I had for on v16.
Thanks,
M.
[0] https://lore.kernel.org/r/20210202141204.3134855-1-maz@kernel.org
--
Jazz is not dead. It just smells funny...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Jianyong Wu <jianyong.wu@arm.com>
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, steven.price@arm.com,
Andre.Przywara@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
Subject: Re: [PATCH v16 0/9] Enable ptp_kvm for arm/arm64
Date: Tue, 02 Feb 2021 14:15:15 +0000 [thread overview]
Message-ID: <74108ee1d0021acbdd7aed5b467e5432@kernel.org> (raw)
In-Reply-To: <20201209060932.212364-1-jianyong.wu@arm.com>
On 2020-12-09 06:09, Jianyong Wu wrote:
> Currently, we offen use ntp (sync time with remote network clock)
> to sync time in VM. But the precision of ntp is subject to network
> delay
> so it's difficult to sync time in a high precision.
>
> kvm virtual ptp clock (ptp_kvm) offers another way to sync time in VM,
> as the remote clock locates in the host instead of remote network
> clock.
> It targets to sync time between guest and host in virtualization
> environment and in this way, we can keep the time of all the VMs
> running
> in the same host in sync. In general, the delay of communication
> between
> host and guest is quiet small, so ptp_kvm can offer time sync precision
> up to in order of nanosecond. Please keep in mind that ptp_kvm just
> limits itself to be a channel which transmit the remote clock from
> host to guest and leaves the time sync jobs to an application, eg.
> chrony,
> in usersapce in VM.
>
> How ptp_kvm works:
> After ptp_kvm initialized, there will be a new device node under
> /dev called ptp%d. A guest userspace service, like chrony, can use this
> device to get host walltime, sometimes also counter cycle, which
> depends
> on the service it calls. Then this guest userspace service can use
> those
> data to do the time sync for guest.
> here is a rough sketch to show how kvm ptp clock works.
>
> |----------------------------|
> |--------------------------|
> | guest userspace | | host
> |
> |ioctl -> /dev/ptp%d | |
> |
> | ^ | | |
> |
> |----------------------------| |
> |
> | | | guest kernel | |
> |
> | | V (get host walltime/counter cycle)
> |
> | ptp_kvm -> hypercall - - - - - - - - - - ->hypercall service
> |
> | <- - - - - - - - - - - -
> |
> |----------------------------|
> |--------------------------|
>
> 1. time sync service in guest userspace call ptp device through
> /dev/ptp%d.
> 2. ptp_kvm module in guest receives this request then invoke hypercall
> to route
> into host kernel to request host walltime/counter cycle.
> 3. ptp_kvm hypercall service in host response to the request and send
> data back.
> 4. ptp (not ptp_kvm) in guest copy the data to userspace.
>
> This ptp_kvm implementation focuses itself to step 2 and 3 and step 2
> works
> in guest comparing step 3 works in host kernel.
FWIW, and in order to speed up the review, I've posted a reworked
version[0] of this series with changes that address the comments
I had for on v16.
Thanks,
M.
[0] https://lore.kernel.org/r/20210202141204.3134855-1-maz@kernel.org
--
Jazz is not dead. It just smells funny...
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: netdev@vger.kernel.org, yangbo.lu@nxp.com,
john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com,
richardcochran@gmail.com, Mark.Rutland@arm.com, will@kernel.org,
suzuki.poulose@arm.com, Andre.Przywara@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 v16 0/9] Enable ptp_kvm for arm/arm64
Date: Tue, 02 Feb 2021 14:15:15 +0000 [thread overview]
Message-ID: <74108ee1d0021acbdd7aed5b467e5432@kernel.org> (raw)
In-Reply-To: <20201209060932.212364-1-jianyong.wu@arm.com>
On 2020-12-09 06:09, Jianyong Wu wrote:
> Currently, we offen use ntp (sync time with remote network clock)
> to sync time in VM. But the precision of ntp is subject to network
> delay
> so it's difficult to sync time in a high precision.
>
> kvm virtual ptp clock (ptp_kvm) offers another way to sync time in VM,
> as the remote clock locates in the host instead of remote network
> clock.
> It targets to sync time between guest and host in virtualization
> environment and in this way, we can keep the time of all the VMs
> running
> in the same host in sync. In general, the delay of communication
> between
> host and guest is quiet small, so ptp_kvm can offer time sync precision
> up to in order of nanosecond. Please keep in mind that ptp_kvm just
> limits itself to be a channel which transmit the remote clock from
> host to guest and leaves the time sync jobs to an application, eg.
> chrony,
> in usersapce in VM.
>
> How ptp_kvm works:
> After ptp_kvm initialized, there will be a new device node under
> /dev called ptp%d. A guest userspace service, like chrony, can use this
> device to get host walltime, sometimes also counter cycle, which
> depends
> on the service it calls. Then this guest userspace service can use
> those
> data to do the time sync for guest.
> here is a rough sketch to show how kvm ptp clock works.
>
> |----------------------------|
> |--------------------------|
> | guest userspace | | host
> |
> |ioctl -> /dev/ptp%d | |
> |
> | ^ | | |
> |
> |----------------------------| |
> |
> | | | guest kernel | |
> |
> | | V (get host walltime/counter cycle)
> |
> | ptp_kvm -> hypercall - - - - - - - - - - ->hypercall service
> |
> | <- - - - - - - - - - - -
> |
> |----------------------------|
> |--------------------------|
>
> 1. time sync service in guest userspace call ptp device through
> /dev/ptp%d.
> 2. ptp_kvm module in guest receives this request then invoke hypercall
> to route
> into host kernel to request host walltime/counter cycle.
> 3. ptp_kvm hypercall service in host response to the request and send
> data back.
> 4. ptp (not ptp_kvm) in guest copy the data to userspace.
>
> This ptp_kvm implementation focuses itself to step 2 and 3 and step 2
> works
> in guest comparing step 3 works in host kernel.
FWIW, and in order to speed up the review, I've posted a reworked
version[0] of this series with changes that address the comments
I had for on v16.
Thanks,
M.
[0] https://lore.kernel.org/r/20210202141204.3134855-1-maz@kernel.org
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2021-02-02 14:15 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 6:09 [PATCH v16 0/9] Enable ptp_kvm for arm/arm64 Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` [PATCH v16 1/9] arm64: Probe for the presence of KVM hypervisor Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2021-02-02 13:18 ` Marc Zyngier
2021-02-02 13:18 ` Marc Zyngier
2021-02-02 13:18 ` Marc Zyngier
2020-12-09 6:09 ` [PATCH v16 2/9] arm/arm64: KVM: Advertise KVM UID to guests via SMCCC Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` [PATCH v16 3/9] ptp: Reorganize ptp_kvm module to make it arch-independent Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 10:23 ` kernel test robot
2020-12-09 10:23 ` kernel test robot
2020-12-09 10:23 ` [RFC PATCH] ptp: clock_pair_gpa can be static kernel test robot
2020-12-09 10:23 ` kernel test robot
2021-02-02 13:23 ` [PATCH v16 3/9] ptp: Reorganize ptp_kvm module to make it arch-independent Marc Zyngier
2021-02-02 13:23 ` Marc Zyngier
2021-02-02 13:23 ` Marc Zyngier
2020-12-09 6:09 ` [PATCH v16 4/9] time: Add mechanism to recognize clocksource in time_get_snapshot Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` [PATCH v16 5/9] clocksource: Add clocksource id for arm arch counter Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` [PATCH v16 6/9] arm64/kvm: Add hypercall service for kvm ptp Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2021-02-02 13:32 ` Marc Zyngier
2021-02-02 13:32 ` Marc Zyngier
2021-02-02 13:32 ` Marc Zyngier
2020-12-09 6:09 ` [PATCH v16 7/9] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2021-02-02 13:37 ` Marc Zyngier
2021-02-02 13:37 ` Marc Zyngier
2021-02-02 13:37 ` Marc Zyngier
2020-12-09 6:09 ` [PATCH v16 8/9] doc: add ptp_kvm introduction for arm64 support Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2021-02-02 13:43 ` Marc Zyngier
2021-02-02 13:43 ` Marc Zyngier
2021-02-02 13:43 ` Marc Zyngier
2020-12-09 6:09 ` [PATCH v16 9/9] arm64: Add kvm capability check extension for ptp_kvm Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2020-12-09 6:09 ` Jianyong Wu
2021-02-02 13:44 ` Marc Zyngier
2021-02-02 13:44 ` Marc Zyngier
2021-02-02 13:44 ` Marc Zyngier
2021-01-06 8:29 ` [PATCH v16 0/9] Enable ptp_kvm for arm/arm64 Jianyong Wu
2021-01-06 8:29 ` Jianyong Wu
2021-01-06 8:29 ` Jianyong Wu
2021-02-02 14:15 ` Marc Zyngier [this message]
2021-02-02 14:15 ` Marc Zyngier
2021-02-02 14:15 ` Marc Zyngier
2021-02-03 2:40 ` Jianyong Wu
2021-02-03 2:40 ` Jianyong Wu
2021-02-03 2:40 ` Jianyong Wu
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