Hi all, This patch series picks up the LPT pvtime feature originally developed by Steven Price: https://patchwork.kernel.org/cover/10726499/ Backgroud: There is demand for cross-platform migration, which means we have to solve different CPU features and arch counter frequency between hosts. This patch series can solve the latter problem. About LPT: This implements support for Live Physical Time (LPT) which provides the guest with a method to derive a stable counter of time during which the guest is executing even when the guest is being migrated between hosts with different physical counter frequencies. Changes on Steven Price's work: 1. LPT structure: use symmatical semantics of scale multiplier, and use fraction bits instead of "shift" to make everything clear. 2. Structure allocation: host kernel does not allocates the LPT structure, instead it is allocated by userspace through VM attributes. The save/restore functionality can be removed. 3. Since LPT structure just need update once for each guest run, add a flag to indicate the update status. This has two benifits: 1) avoid multiple update by each vCPUs. 2) If the update flag is not set, then return NOT SUPPORT for coressponding guest HVC call. 4. Add VM device attributes interface for userspace configuration. 5. Add a base LPT read/write layer to reduce code. 6. Support ptimer scaling. 7. Support timer event stream translation. Things need concern: 1. https://developer.arm.com/docs/den0057/a needs update. 2. If a guest fails to initialize and use LPT, when it migrates to a host with different native frequency, it will see the virtual counter jump. However this concern is not a problem. 1) Guest does not support LPT or host does not enable LPT: we won't migrate guest to a host with different frequency. 2) Guest kernel faces problem when initilize LPT: guest can not boot up, so counter jump is not a problem at this situation. Patch 2 and 3 implement host KVM part. Patch 4 and 5 implement guest driver part. Keqian Zhu (5): KVM: arm64: Document pvtime LPT interface KVM: arm64: Support Live Physical Time reporting KVM: arm64: Provide VM device attributes for LPT time clocksource: arm_arch_timer: Add pvtime LPT initialization clocksource: arm_arch_timer: Use pvtime LPT Documentation/virt/kvm/arm/pvtime.rst | 78 +++++++++++-- Documentation/virt/kvm/devices/vm.rst | 30 +++++ arch/arm64/include/asm/arch_timer.h | 179 ++++++++++++++++++++++++++-- arch/arm64/include/asm/kvm_host.h | 14 +++ arch/arm64/include/uapi/asm/kvm.h | 5 + arch/arm64/kvm/arm.c | 71 ++++++++++++ arch/arm64/kvm/hypercalls.c | 5 + arch/arm64/kvm/pvtime.c | 212 +++++++++++++++++++++++++++++++++- drivers/clocksource/arm_arch_timer.c | 120 +++++++++++++++---- 9 files changed, 669 insertions(+), 45 deletions(-) -- 1.8.3.1
