On 2021/3/30 22:54, Marc Zyngier wrote:

+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

Per include/linux/arm-smccc.h, this should be
ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID.

+
+This hypercall uses the SMC32/HVC32 calling convention:
+
+ARM_SMCCC_HYP_KVM_PTP_FUNC_ID

ditto

+    =============    ==========    ==========
+    Function ID:     (uint32)      0x86000001
+    Arguments:       (uint32)      KVM_PTP_VIRT_COUNTER(0)
+                                   KVM_PTP_PHYS_COUNTER(1)