Introduce a paravirtualization interface for KVM/arm64 to obtain the VCPU is currently running or not. The PV lock structure of the guest is allocated by user space. A hypercall interface is provided for the guest to interrogate the hypervisor's support for this interface and the location of the shared memory structures. Signed-off-by: Zengruan Ye <yezengruan@xxxxxxxxxx> --- Documentation/virt/kvm/arm/pvlock.rst | 63 +++++++++++++++++++++++++ Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++ 2 files changed, 77 insertions(+) create mode 100644 Documentation/virt/kvm/arm/pvlock.rst diff --git a/Documentation/virt/kvm/arm/pvlock.rst b/Documentation/virt/kvm/arm/pvlock.rst new file mode 100644 index 000000000000..58b3b8ee7537 --- /dev/null +++ b/Documentation/virt/kvm/arm/pvlock.rst @@ -0,0 +1,63 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Paravirtualized lock support for arm64 +====================================== + +KVM/arm64 provides some hypervisor service calls to support a paravirtualized +guest obtaining the VCPU is currently running or not. + +Two new SMCCC compatible hypercalls are defined: + +* PV_LOCK_FEATURES: 0xC6000020 +* PV_LOCK_PREEMPTED: 0xC6000021 + +The existence of the PV_LOCK hypercall should be probed using the SMCCC 1.1 +ARCH_FEATURES mechanism before calling it. + +PV_LOCK_FEATURES + ============= ======== ========== + Function ID: (uint32) 0xC6000020 + PV_call_id: (uint32) The function to query for support. + Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant + PV-lock feature is supported by the hypervisor. + ============= ======== ========== + +PV_LOCK_PREEMPTED + ============= ======== ========== + Function ID: (uint32) 0xC6000021 + Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the IPA of + this VCPU's pv data structure is configured by + the hypervisor. + ============= ======== ========== + +The IPA returned by PV_LOCK_PREEMPTED should be mapped by the guest as normal +memory with inner and outer write back caching attributes, in the inner +shareable domain. + +PV_LOCK_PREEMPTED returns the structure for the calling VCPU. + +PV lock state +------------- + +The structure pointed to by the PV_LOCK_PREEMPTED hypercall is as follows: + ++-----------+-------------+-------------+---------------------------------+ +| Field | Byte Length | Byte Offset | Description | ++===========+=============+=============+=================================+ +| preempted | 8 | 0 | Indicate the VCPU who owns this | +| | | | struct is running or not. | +| | | | Non-zero values mean the VCPU | +| | | | has been preempted. Zero means | +| | | | the VCPU is not preempted. | ++-----------+-------------+-------------+---------------------------------+ + +The preempted field will be updated to 1 by the hypervisor prior to scheduling +a VCPU. When the VCPU is scheduled out, the preempted field will be updated +to 0 by the hypervisor. + +The structure 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 VCPU of the guest. + +For the user space interface see Documentation/virt/kvm/devices/vcpu.txt +section "4. GROUP: KVM_ARM_VCPU_PVLOCK_CTRL". diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt index 6f3bd64a05b0..c10a5945075b 100644 --- a/Documentation/virt/kvm/devices/vcpu.txt +++ b/Documentation/virt/kvm/devices/vcpu.txt @@ -74,3 +74,17 @@ Specifies the base address of the stolen time structure for this VCPU. The base address must be 64 byte aligned and exist within a valid guest memory region. See Documentation/virt/kvm/arm/pvtime.txt for more information including the layout of the stolen time structure. + +4. GROUP: KVM_ARM_VCPU_PVLOCK_CTRL +Architectures: ARM64 + +4.1 ATTRIBUTE: KVM_ARM_VCPU_PVLOCK_IPA +Parameters: 64-bit base address +Returns: -ENXIO: PV lock not implemented + -EEXIST: Base address already set for this VCPU + -EINVAL: Base address not 64 byte aligned + +Specifies the base address of the PV lock structure for this VCPU. The +base address must be 64 byte aligned and exist within a valid guest memory +region. See Documentation/virt/kvm/arm/pvlock.rst for more information +including the layout of the pv lock structure. -- 2.19.1 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
