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| author | Jianyong Wu <jianyong.wu@arm.com> | 2020-12-09 14:09:29 +0800 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2021-04-07 16:33:20 +0100 |
| commit | 3bf725699bf62494b3e179f1795f08c7d749f061 (patch) | |
| tree | b2f880f70fd927e430b06c2a8e5c3b35ad672fe9 /Documentation/virt/kvm/arm/ptp_kvm.rst | |
| parent | 100148d0fc7dcf8672fe0ac83f44dc5749b4da5c (diff) | |
| download | linux-stable-3bf725699bf62494b3e179f1795f08c7d749f061.tar.gz linux-stable-3bf725699bf62494b3e179f1795f08c7d749f061.tar.bz2 linux-stable-3bf725699bf62494b3e179f1795f08c7d749f061.zip | |
KVM: arm64: Add support for the KVM PTP service
Implement the hypervisor side of the KVM PTP interface.
The service offers wall time and cycle count from host to guest.
The caller must specify whether they want the host's view of
either the virtual or physical counter.
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-7-jianyong.wu@arm.com
Diffstat (limited to 'Documentation/virt/kvm/arm/ptp_kvm.rst')
| -rw-r--r-- | Documentation/virt/kvm/arm/ptp_kvm.rst | 25 |
1 files changed, 25 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..68cffb50d8bf --- /dev/null +++ b/Documentation/virt/kvm/arm/ptp_kvm.rst @@ -0,0 +1,25 @@ +.. 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_HYP_KVM_PTP_FUNC_ID: 0x86000001 + +This hypercall uses the SMC32/HVC32 calling convention: + +ARM_SMCCC_HYP_KVM_PTP_FUNC_ID + ============= ========== ========== + Function ID: (uint32) 0x86000001 + Arguments: (uint32) KVM_PTP_VIRT_COUNTER(0) + KVM_PTP_PHYS_COUNTER(1) + Return Values: (int32) NOT_SUPPORTED(-1) on error, or + (uint32) Upper 32 bits of wall clock time (r0) + (uint32) Lower 32 bits of wall clock time (r1) + (uint32) Upper 32 bits of counter (r2) + (uint32) Lower 32 bits of counter (r3) + Endianness: No Restrictions. + ============= ========== ========== |