Ping... Any comments? Thanks! > -----Original Message----- > From: Jianyong Wu <jianyong.wu@xxxxxxx> > Sent: Wednesday, December 9, 2020 2:09 PM > To: netdev@xxxxxxxxxxxxxxx; yangbo.lu@xxxxxxx; john.stultz@xxxxxxxxxx; > tglx@xxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; sean.j.christopherson@xxxxxxxxx; > maz@xxxxxxxxxx; richardcochran@xxxxxxxxx; Mark Rutland > <Mark.Rutland@xxxxxxx>; will@xxxxxxxxxx; Suzuki Poulose > <Suzuki.Poulose@xxxxxxx>; Andre Przywara <Andre.Przywara@xxxxxxx>; > Steven Price <Steven.Price@xxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Steve Capper > <Steve.Capper@xxxxxxx>; Justin He <Justin.He@xxxxxxx>; Jianyong Wu > <Jianyong.Wu@xxxxxxx>; nd <nd@xxxxxxx> > Subject: [PATCH v16 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 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. > > change log: > > from v15 to v16: > (1) remove ARM_PTP_NONE_COUNTER suggested by Marc. > (2) add more detail for ptp_kvm doc. > (3) fix ci issues reported by test robot. > > 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 | 31 +++++++ > Documentation/virt/kvm/timekeeping.rst | 35 ++++++++ > arch/arm/kernel/setup.c | 5 ++ > arch/arm64/kernel/setup.c | 1 + > arch/arm64/kvm/arm.c | 1 + > arch/arm64/kvm/hypercalls.c | 86 ++++++++++++++++-- > drivers/clocksource/arm_arch_timer.c | 31 +++++++ > drivers/firmware/smccc/smccc.c | 37 ++++++++ > drivers/ptp/Kconfig | 2 +- > drivers/ptp/Makefile | 2 + > drivers/ptp/ptp_kvm_arm.c | 45 ++++++++++ > drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} | 84 +++++------------- > drivers/ptp/ptp_kvm_x86.c | 96 +++++++++++++++++++++ > include/linux/arm-smccc.h | 59 +++++++++++++ > include/linux/clocksource.h | 6 ++ > include/linux/clocksource_ids.h | 12 +++ > include/linux/ptp_kvm.h | 16 ++++ > include/linux/timekeeping.h | 12 +-- > include/uapi/linux/kvm.h | 1 + > kernel/time/clocksource.c | 2 + > kernel/time/timekeeping.c | 1 + > 23 files changed, 498 insertions(+), 77 deletions(-) create mode 100644 > Documentation/virt/kvm/arm/ptp_kvm.rst > 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 create mode 100644 > include/linux/ptp_kvm.h > > -- > 2.17.1
