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Diffstat (limited to 'Documentation/virt/kvm/arm/ptp_kvm.rst')
| -rw-r--r-- | Documentation/virt/kvm/arm/ptp_kvm.rst | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/arm/ptp_kvm.rst b/Documentation/virt/kvm/arm/ptp_kvm.rst new file mode 100644 index 000000000000..7c0960970a0e --- /dev/null +++ b/Documentation/virt/kvm/arm/ptp_kvm.rst @@ -0,0 +1,35 @@ +.. SPDX-License-Identifier: GPL-2.0 + +PTP_KVM support for arm/arm64 +============================= + +PTP_KVM is used for high precision time sync between host and guests. +It relies on transferring the wall clock and counter value from the +host to the guest using a KVM-specific hypercall. + +``ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID`` +---------------------------------------- + +Retrieve current time information for the specific counter. There are no +endianness restrictions. + ++---------------------+-------------------------------------------------------+ +| Presence: | Optional | ++---------------------+-------------------------------------------------------+ +| Calling convention: | HVC32 | ++---------------------+----------+--------------------------------------------+ +| Function ID: | (uint32) | 0x86000001 | ++---------------------+----------+----+---------------------------------------+ +| Arguments: | (uint32) | R1 | ``KVM_PTP_VIRT_COUNTER (0)`` | +| | | +---------------------------------------+ +| | | | ``KVM_PTP_PHYS_COUNTER (1)`` | ++---------------------+----------+----+---------------------------------------+ +| Return Values: | (int32) | R0 | ``NOT_SUPPORTED (-1)`` on error, else | +| | | | upper 32 bits of wall clock time | +| +----------+----+---------------------------------------+ +| | (uint32) | R1 | Lower 32 bits of wall clock time | +| +----------+----+---------------------------------------+ +| | (uint32) | R2 | Upper 32 bits of counter | +| +----------+----+---------------------------------------+ +| | (uint32) | R3 | Lower 32 bits of counter | ++---------------------+----------+----+---------------------------------------+ |