| Message ID | 20201111062211.33144-1-jianyong.wu@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Enable ptp_kvm for arm/arm64 | expand |
Hi, Ping ... Any comments? > -----Original Message----- > From: Jianyong Wu <jianyong.wu@arm.com> > Sent: Wednesday, November 11, 2020 2:22 PM > To: netdev@vger.kernel.org; yangbo.lu@nxp.com; john.stultz@linaro.org; > tglx@linutronix.de; pbonzini@redhat.com; sean.j.christopherson@intel.com; > maz@kernel.org; richardcochran@gmail.com; Mark Rutland > <Mark.Rutland@arm.com>; will@kernel.org; Suzuki Poulose > <Suzuki.Poulose@arm.com>; Andre Przywara <Andre.Przywara@arm.com>; > Steven Price <Steven.Price@arm.com> > Cc: linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; > kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org; Steve Capper > <Steve.Capper@arm.com>; Justin He <Justin.He@arm.com>; Jianyong Wu > <Jianyong.Wu@arm.com>; nd <nd@arm.com> > Subject: [PATCH v15 0/9] Enable ptp_kvm for arm/arm64 > > 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 recive 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. > > change log: > > from v14 to v15 > (1) enable ptp_kvm on arm32 guest, also ptp_kvm has been tested on > both arm64 and arm32 guest running on arm64 kvm host. > (2) move arch-agnostic part of ptp_kvm.rst into timekeeping.rst. > (3) rename KVM_CAP_ARM_PTP_KVM to KVM_CAP_PTP_KVM as it > should be arch agnostic. > (4) add description for KVM_CAP_PTP_KVM in > Documentation/virt/kvm/api.rst. > (5) adjust dependency in Kconfig for ptp_kvm. > (6) refine multi-arch process in driver/ptp/Makefile. > (7) fix make pdfdocs htmldocs issue for ptp_kvm doc. > (8) address other issues from comments in v14. > (9) fold hypercall service of ptp_kvm as a function. > (10) rebase to 5.10-rc3. > > from v13 to v14 > (1) rebase code on 5.9-rc3. > (2) add a document to introduce implementation of PTP_KVM on arm64. > (3) fix comments issue in hypercall.c. > (4) export arm_smccc_1_1_get_conduit using EXPORT_SYMBOL_GPL. > (5) fix make issue on x86 reported by kernel test robot. > > from v12 to v13: > (1) rebase code on 5.8-rc1. > (2) this patch set base on 2 patches of 1/8 and 2/8 from Will Decon. > (3) remove the change to ptp device code of extend getcrosststamp. > (4) remove the mechanism of letting user choose the counter type in > ptp_kvm for arm64. > (5) add virtual counter option in ptp_kvm service to let user choose the > specific counter explicitly. > > from v11 to v12: > (1) rebase code on 5.7-rc6 and rebase 2 patches from Will Decon > including 1/11 and 2/11. as these patches introduce discover mechanism of > vendor smccc service. > (2) rebase ptp_kvm hypercall service from standard smccc to vendor > smccc and add ptp_kvm to vendor smccc service discover mechanism. > (3) add detail of why we need ptp_kvm and how ptp_kvm works in cover > letter. > > from v10 to v11: > (1) rebase code on 5.7-rc2. > (2) remove support for arm32, as kvm support for arm32 will be removed > [1] > (3) add error report in ptp_kvm initialization. > > from v9 to v10: > (1) change code base to v5.5. > (2) enable ptp_kvm both for arm32 and arm64. > (3) let user choose which of virtual counter or physical counter should > return when using crosstimestamp mode of ptp_kvm for arm/arm64. > (4) extend input argument for getcrosstimestamp API. > > from v8 to v9: > (1) move ptp_kvm.h to driver/ptp/ > (2) replace license declaration of ptp_kvm.h the same with other header > files in the same directory. > > from v7 to v8: > (1) separate adding clocksource id for arm_arch_counter as a single patch. > (2) update commit message for patch 4/8. > (3) refine patch 7/8 and patch 8/8 to make them more independent. > > from v5 to v6: > (1) apply Mark's patch[4] to get SMCCC conduit. > (2) add mechanism to recognize current clocksource by add > clocksouce_id value into struct clocksource instead of method in patch-v5. > (3) rename kvm_arch_ptp_get_clock_fn into > kvm_arch_ptp_get_crosststamp. > > from v4 to v5: > (1) remove hvc delay compensasion as it should leave to userspace. > (2) check current clocksource in hvc call service. > (3) expose current clocksource by adding it to system_time_snapshot. > (4) add helper to check if clocksource is arm_arch_counter. > (5) rename kvm_ptp.c to ptp_kvm_common.c > > from v3 to v4: > (1) fix clocksource of ptp_kvm to arch_sys_counter. > (2) move kvm_arch_ptp_get_clock_fn into arm_arch_timer.c > (3) subtract cntvoff before return cycles from host. > (4) use ktime_get_snapshot instead of getnstimeofday and > get_current_counterval to return time and counter value. > (5) split ktime and counter into two 32-bit block respectively to avoid > Y2038-safe issue. > (6) set time compensation to device time as half of the delay of hvc call. > (7) add ARM_ARCH_TIMER as dependency of ptp_kvm for arm64. > > from v2 to v3: > (1) fix some issues in commit log. > (2) add some receivers in send list. > > from v1 to v2: > (1) move arch-specific code from arch/ to driver/ptp/ > (2) offer mechanism to inform userspace if ptp_kvm service is available. > (3) separate ptp_kvm code for arm64 into hypervisor part and guest part. > (4) add API to expose monotonic clock and counter value. > (5) refine code: remove no necessary part and reconsitution. > > [1] https://patchwork.kernel.org/cover/11373351/ > > > Jianyong Wu (6): > ptp: Reorganize ptp_kvm module to make it arch-independent. > clocksource: Add clocksource id for arm arch counter > arm64/kvm: Add hypercall service for kvm ptp. > ptp: arm/arm64: Enable ptp_kvm for arm/arm64 > doc: add ptp_kvm introduction for arm64 support > arm64: Add kvm capability check extension for ptp_kvm > > Thomas Gleixner (1): > time: Add mechanism to recognize clocksource in time_get_snapshot > > Will Deacon (2): > arm64: Probe for the presence of KVM hypervisor > arm/arm64: KVM: Advertise KVM UID to guests via SMCCC > > Documentation/virt/kvm/api.rst | 9 ++ > Documentation/virt/kvm/arm/index.rst | 1 + > Documentation/virt/kvm/arm/ptp_kvm.rst | 29 +++++++ > Documentation/virt/kvm/timekeeping.rst | 35 ++++++++ > arch/arm/kernel/setup.c | 1 + > arch/arm64/kernel/setup.c | 1 + > arch/arm64/kvm/arm.c | 1 + > arch/arm64/kvm/hypercalls.c | 88 +++++++++++++++++-- > drivers/clocksource/arm_arch_timer.c | 30 +++++++ > drivers/firmware/smccc/smccc.c | 37 ++++++++ > drivers/ptp/Kconfig | 2 +- > drivers/ptp/Makefile | 2 + > drivers/ptp/ptp_kvm.h | 11 +++ > drivers/ptp/ptp_kvm_arm.c | 44 ++++++++++ > drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} | 85 +++++------------- > drivers/ptp/ptp_kvm_x86.c | 95 +++++++++++++++++++++ > include/linux/arm-smccc.h | 60 +++++++++++++ > include/linux/clocksource.h | 6 ++ > include/linux/clocksource_ids.h | 12 +++ > include/linux/timekeeping.h | 12 +-- > include/uapi/linux/kvm.h | 1 + > kernel/time/clocksource.c | 2 + > kernel/time/timekeeping.c | 1 + > 23 files changed, 488 insertions(+), 77 deletions(-) create mode 100644 > Documentation/virt/kvm/arm/ptp_kvm.rst > create mode 100644 drivers/ptp/ptp_kvm.h create mode 100644 > drivers/ptp/ptp_kvm_arm.c rename drivers/ptp/{ptp_kvm.c => > ptp_kvm_common.c} (60%) create mode 100644 > drivers/ptp/ptp_kvm_x86.c create mode 100644 > include/linux/clocksource_ids.h > > -- > 2.17.1
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 recive 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. change log: from v14 to v15 (1) enable ptp_kvm on arm32 guest, also ptp_kvm has been tested on both arm64 and arm32 guest running on arm64 kvm host. (2) move arch-agnostic part of ptp_kvm.rst into timekeeping.rst. (3) rename KVM_CAP_ARM_PTP_KVM to KVM_CAP_PTP_KVM as it should be arch agnostic. (4) add description for KVM_CAP_PTP_KVM in Documentation/virt/kvm/api.rst. (5) adjust dependency in Kconfig for ptp_kvm. (6) refine multi-arch process in driver/ptp/Makefile. (7) fix make pdfdocs htmldocs issue for ptp_kvm doc. (8) address other issues from comments in v14. (9) fold hypercall service of ptp_kvm as a function. (10) rebase to 5.10-rc3. from v13 to v14 (1) rebase code on 5.9-rc3. (2) add a document to introduce implementation of PTP_KVM on arm64. (3) fix comments issue in hypercall.c. (4) export arm_smccc_1_1_get_conduit using EXPORT_SYMBOL_GPL. (5) fix make issue on x86 reported by kernel test robot. from v12 to v13: (1) rebase code on 5.8-rc1. (2) this patch set base on 2 patches of 1/8 and 2/8 from Will Decon. (3) remove the change to ptp device code of extend getcrosststamp. (4) remove the mechanism of letting user choose the counter type in ptp_kvm for arm64. (5) add virtual counter option in ptp_kvm service to let user choose the specific counter explicitly. from v11 to v12: (1) rebase code on 5.7-rc6 and rebase 2 patches from Will Decon including 1/11 and 2/11. as these patches introduce discover mechanism of vendor smccc service. (2) rebase ptp_kvm hypercall service from standard smccc to vendor smccc and add ptp_kvm to vendor smccc service discover mechanism. (3) add detail of why we need ptp_kvm and how ptp_kvm works in cover letter. from v10 to v11: (1) rebase code on 5.7-rc2. (2) remove support for arm32, as kvm support for arm32 will be removed [1] (3) add error report in ptp_kvm initialization. from v9 to v10: (1) change code base to v5.5. (2) enable ptp_kvm both for arm32 and arm64. (3) let user choose which of virtual counter or physical counter should return when using crosstimestamp mode of ptp_kvm for arm/arm64. (4) extend input argument for getcrosstimestamp API. from v8 to v9: (1) move ptp_kvm.h to driver/ptp/ (2) replace license declaration of ptp_kvm.h the same with other header files in the same directory. from v7 to v8: (1) separate adding clocksource id for arm_arch_counter as a single patch. (2) update commit message for patch 4/8. (3) refine patch 7/8 and patch 8/8 to make them more independent. from v5 to v6: (1) apply Mark's patch[4] to get SMCCC conduit. (2) add mechanism to recognize current clocksource by add clocksouce_id value into struct clocksource instead of method in patch-v5. (3) rename kvm_arch_ptp_get_clock_fn into kvm_arch_ptp_get_crosststamp. from v4 to v5: (1) remove hvc delay compensasion as it should leave to userspace. (2) check current clocksource in hvc call service. (3) expose current clocksource by adding it to system_time_snapshot. (4) add helper to check if clocksource is arm_arch_counter. (5) rename kvm_ptp.c to ptp_kvm_common.c from v3 to v4: (1) fix clocksource of ptp_kvm to arch_sys_counter. (2) move kvm_arch_ptp_get_clock_fn into arm_arch_timer.c (3) subtract cntvoff before return cycles from host. (4) use ktime_get_snapshot instead of getnstimeofday and get_current_counterval to return time and counter value. (5) split ktime and counter into two 32-bit block respectively to avoid Y2038-safe issue. (6) set time compensation to device time as half of the delay of hvc call. (7) add ARM_ARCH_TIMER as dependency of ptp_kvm for arm64. from v2 to v3: (1) fix some issues in commit log. (2) add some receivers in send list. from v1 to v2: (1) move arch-specific code from arch/ to driver/ptp/ (2) offer mechanism to inform userspace if ptp_kvm service is available. (3) separate ptp_kvm code for arm64 into hypervisor part and guest part. (4) add API to expose monotonic clock and counter value. (5) refine code: remove no necessary part and reconsitution. [1] https://patchwork.kernel.org/cover/11373351/ Jianyong Wu (6): ptp: Reorganize ptp_kvm module to make it arch-independent. clocksource: Add clocksource id for arm arch counter arm64/kvm: Add hypercall service for kvm ptp. ptp: arm/arm64: Enable ptp_kvm for arm/arm64 doc: add ptp_kvm introduction for arm64 support arm64: Add kvm capability check extension for ptp_kvm Thomas Gleixner (1): time: Add mechanism to recognize clocksource in time_get_snapshot Will Deacon (2): arm64: Probe for the presence of KVM hypervisor arm/arm64: KVM: Advertise KVM UID to guests via SMCCC Documentation/virt/kvm/api.rst | 9 ++ Documentation/virt/kvm/arm/index.rst | 1 + Documentation/virt/kvm/arm/ptp_kvm.rst | 29 +++++++ Documentation/virt/kvm/timekeeping.rst | 35 ++++++++ arch/arm/kernel/setup.c | 1 + arch/arm64/kernel/setup.c | 1 + arch/arm64/kvm/arm.c | 1 + arch/arm64/kvm/hypercalls.c | 88 +++++++++++++++++-- drivers/clocksource/arm_arch_timer.c | 30 +++++++ drivers/firmware/smccc/smccc.c | 37 ++++++++ drivers/ptp/Kconfig | 2 +- drivers/ptp/Makefile | 2 + drivers/ptp/ptp_kvm.h | 11 +++ drivers/ptp/ptp_kvm_arm.c | 44 ++++++++++ drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} | 85 +++++------------- drivers/ptp/ptp_kvm_x86.c | 95 +++++++++++++++++++++ include/linux/arm-smccc.h | 60 +++++++++++++ include/linux/clocksource.h | 6 ++ include/linux/clocksource_ids.h | 12 +++ include/linux/timekeeping.h | 12 +-- include/uapi/linux/kvm.h | 1 + kernel/time/clocksource.c | 2 + kernel/time/timekeeping.c | 1 + 23 files changed, 488 insertions(+), 77 deletions(-) create mode 100644 Documentation/virt/kvm/arm/ptp_kvm.rst create mode 100644 drivers/ptp/ptp_kvm.h create mode 100644 drivers/ptp/ptp_kvm_arm.c rename drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} (60%) create mode 100644 drivers/ptp/ptp_kvm_x86.c create mode 100644 include/linux/clocksource_ids.h