5.3.18 GetNextHighMonotonicCount()
There are no use cases for this service by a UEFI Driver. It should never be called.
This service is only used by operating systems to manage the upper 32-bits of
the 64-bit monotonic counter after the operating system has called
ExitBootServices()
. An operating system that chooses to use the UEFI provided
64-bit monotonic counter should acquire the value of the 64-bit monotonic
counter before ExitBootServices()
using the UEFI Boot Service
GetNextMonotonicCount()
. The operating system can manage the volatile lower
32-bits of the 64-bit monotonic counter on its own. If a 32bit rollover
condition occurs, then the operating system can use the UEFI Runtime Service
GetNextHighMonotonicCount()
to increment the upper 32-bits of the 64-bit
monotonic counter. The upper 32-bits are non-volatile and it is the
responsibility of the UEFI firmware to guarantee that the upper 32-bits of the
64-bit monotonic counter are preserved across system resets and power cycles.