The "Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A just contains "Stolen Time" now, as the details of "Live Physical Time" have not been fully agreed. This introduces a new LPT structure with more understandable fields, as scale_mult and rscale_mult are symmetrical. Signed-off-by: Steven Price <steven.price@xxxxxxx> Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx> --- Documentation/virt/kvm/arm/pvtime.rst | 78 ++++++++++++++++++++++++++++++----- Documentation/virt/kvm/devices/vm.rst | 30 ++++++++++++++ 2 files changed, 97 insertions(+), 11 deletions(-) diff --git a/Documentation/virt/kvm/arm/pvtime.rst b/Documentation/virt/kvm/arm/pvtime.rst index 94bffe2..fd11915 100644 --- a/Documentation/virt/kvm/arm/pvtime.rst +++ b/Documentation/virt/kvm/arm/pvtime.rst @@ -8,14 +8,17 @@ support for AArch64 guests: https://developer.arm.com/docs/den0057/a -KVM/arm64 implements the stolen time part of this specification by providing -some hypervisor service calls to support a paravirtualized guest obtaining a -view of the amount of time stolen from its execution. +KVM/arm64 implements the stolen time and live physical time (LPT) parts of this +specification by providing some hypervisor service calls to a paravirtualized +guest. With stolen time support, guest can obtain the amount of time stolen +from its execution. LPT represents time during which the guest is running and +it realizes cross-native-frequency migrations. -Two new SMCCC compatible hypercalls are defined: +Three new SMCCC compatible hypercalls are defined: * PV_TIME_FEATURES: 0xC5000020 * PV_TIME_ST: 0xC5000021 +* PV_TIME_LPT: 0xC5000022 These are only available in the SMC64/HVC64 calling convention as paravirtualized time is not available to 32 bit Arm guests. The existence of @@ -26,7 +29,8 @@ PV_TIME_FEATURES ============= ======== ========== Function ID: (uint32) 0xC5000020 PV_call_id: (uint32) The function to query for support. - Currently only PV_TIME_ST is supported. + Currently only PV_TIME_ST and PV_TIME_LPT are + supported. Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant PV-time feature is supported by the hypervisor. ============= ======== ========== @@ -39,17 +43,23 @@ PV_TIME_ST NOT_SUPPORTED (-1) ============= ======== ========== -The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory -with inner and outer write back caching attributes, in the inner shareable -domain. A total of 16 bytes from the IPA returned are guaranteed to be -meaningfully filled by the hypervisor (see structure below). +PV_TIME_LPT + ============= ======== ========== + Function ID: (uint32) 0xC5000022 + Return value: (int64) IPA of the LPT data structure for this guest. + On failure: + NOT_SUPPORTED (-1) + ============= ======== ========== -PV_TIME_ST returns the structure for the calling VCPU. +The IPA returned by PV_TIME_ST and PV_TIME_LPT should be mapped by the guest as +normal memory with inner and outer write back caching attributes, in the inner +shareable domain. Stolen Time ----------- -The structure pointed to by the PV_TIME_ST hypercall is as follows: +A total of 16 bytes from the IPA returned are guaranteed to be meaningfully +filled by the hypervisor. The structure description is as follows: +-------------+-------------+-------------+----------------------------+ | Field | Byte Length | Byte Offset | Description | @@ -78,3 +88,49 @@ the region using 64k pages and avoids conflicting attributes with other memory. For the user space interface see Documentation/virt/kvm/devices/vcpu.rst section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL". + +Live Physical Time +----------- + +A total of 48 bytes from the IPA returned are guaranteed to be meaningfully +filled by the hypervisor. The structure description is as follows: + ++-----------------+-------------+-------------+----------------------------+ +| Field | Byte Length | Byte Offset | Description | ++=================+=============+=============+============================+ +| Revision | 4 | 0 | Must be 0 for version 1.0 | ++-----------------+-------------+-------------+----------------------------+ +| Attributes | 4 | 4 | Must be 0 | ++-----------------+-------------+-------------+----------------------------+ +| sequence_number | 8 | 8 | Bit 0: reserved | +| | | | Bits 1-63: number of runs, | +| | | | including the initial run. | ++-----------------+-------------+-------------+----------------------------| +| native_freq | 4 | 16 | Native frequency | ++-----------------+-------------+-------------+----------------------------| +| pv_freq | 4 | 20 | Paravirtualized frequency | +| | | | seen by guest | ++-----------------+-------------+-------------+----------------------------| +| scale_mult | 8 | 24 | Multiplier to scale native | +| | | | cycles to PV cycles | ++-----------------+-------------+-------------+----------------------------| +| rscale_mult | 8 | 32 | Multiplier to reversely | +| | | | scale PV cycles to native | +| | | | cycles | ++-----------------+-------------+-------------+----------------------------| +| fracbits | 4 | 40 | The bits of fraction of | +| | | | scale_mult | ++-----------------+-------------+-------------+----------------------------| +| rfracbits | 4 | 44 | The bits of fraction of | +| | | | rscale_mult | ++-----------------+-------------+-------------+----------------------------| + +All values in the structure are stored little-endian. + +The structure will be updated by the hypervisor prior to scheduling VCPUs. It +will be present within a reserved region of the normal memory given to the +guest. The guest should not attempt to write into this memory. There is a +structure per guest. + +For the user space interface see Documentation/virt/kvm/devices/vm.rst +section "6. GROUP: KVM_ARM_VM_PVTIME_LPT_CTRL". diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst index 0aa5b1c..7e5a189 100644 --- a/Documentation/virt/kvm/devices/vm.rst +++ b/Documentation/virt/kvm/devices/vm.rst @@ -314,3 +314,33 @@ Allows userspace to query the status of migration mode. if it is enabled :Returns: -EFAULT if the given address is not accessible from kernel space; 0 in case of success. + +6. GROUP: KVM_ARM_VM_PVTIME_LPT_CTRL +==================================== + +:Architectures: ARM64 + +6.1. ATTRIBUTE: KVM_ARM_VM_PVTIME_LPT_IPA (r/w) +----------------------------------------------- + +Specifies the base address of the live physical time (LPT) structure for this +guest. The base address must be 64 byte aligned and exist within a valid guest +memory region. See Documentation/virt/kvm/arm/pvtime.rst for more information +including the layout of the LPT structure. + +Parameters: 64-bit base address +Returns: -ENXIO: LPT not implemented + -EEXIST: Base address already set for this guest + -EINVAL: Base address not 64 byte aligned or not within guest memory + +6.2. ATTRIBUTE: KVM_ARM_VM_PVTIME_LPT_FREQ (r/w) +------------------------------------------------ + +Specifies the paravirtualized (PV) frequency for this guest. The PV frequency +is independent with native frequency, so we can support cross-native-frequency +migration. + +Parameters: 32-bit PV frequency +Returns: -ENXIO: LPT not implemented + -EEXIST: PV frequency already set for this guest + -EINVAL: PV frequency is zero -- 1.8.3.1
