diff options
Diffstat (limited to 'Documentation/virt/kvm/arm/ptp_kvm.rst')
| -rw-r--r-- | Documentation/virt/kvm/arm/ptp_kvm.rst | 38 |
1 files changed, 24 insertions, 14 deletions
diff --git a/Documentation/virt/kvm/arm/ptp_kvm.rst b/Documentation/virt/kvm/arm/ptp_kvm.rst index aecdc80ddcd8..7c0960970a0e 100644 --- a/Documentation/virt/kvm/arm/ptp_kvm.rst +++ b/Documentation/virt/kvm/arm/ptp_kvm.rst @@ -7,19 +7,29 @@ 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: 0x86000001 +``ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID`` +---------------------------------------- -This hypercall uses the SMC32/HVC32 calling convention: +Retrieve current time information for the specific counter. There are no +endianness restrictions. -ARM_SMCCC_VENDOR_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. - ============== ======== ===================================== ++---------------------+-------------------------------------------------------+ +| 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 | ++---------------------+----------+----+---------------------------------------+ |