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Volume 2, Part 2: Firmware Overview
2:637
13.3.3
PMI Flows
Processors based on the Itanium architecture implement the Platform Management
Interrupt (PMI) to enable platform developers to provide high level system functions,
such as power management and security, in a manner that is transparent not only to
the application software but also to the operating system.
When the processor detects a PMI event it will transfer control to the registered PAL
PMI entrypoint. PAL will set up the hand off state which includes the vector information
for the PMI and hand off control to the registered SAL PMI handler. To reduce the PMI
overhead time, the PAL PMI handler will not save any processor architectural state to
memory. Please see
Section 11.5, “Platform Management Interrupt (PMI)”
for more
information on PAL PMI handling.
The SAL PMI handler may choose to save some additional register state to SAL
allocated memory to handle the specific platform event that generated the PMI.
The OS will not see the PMI events generated by the platform. The platform developer
can use PMI interrupts to provide features to differentiate their platform.
PMI handling was designed to be executed with minimal overhead. The SAL firmware
code copies the PAL and SAL PMI handlers to RAM during system reset and registers
these entry-points with the processor. This code is then run with the cacheable memory
attribute to improve performance.
Depending on the implementation and the platform, there may be no special hardware
protection of the PMI code's memory area in RAM, and the protection of this code space
may be through the OS memory management’s paging mechanism. SAL sets the
correct attributes for this memory space and passes this information to the OS through
the Memory Descriptor Table from EfiGetMemoryMap() [UEFI].
13.3.4
P-state Feedback Mechanism Flow Diagram
The example flowchart shown below illustrates how the caller can utilize the
PAL_SET_PSTATE and the PAL_GET_PSTATE procedures to manage system utilization
and power consumption, for a processor implementation that belongs to either a
hardware-coordinated dependency domain or a hardware-independent dependency
domain. At the beginning of the loop, PAL_GET_PSTATE gives the performance
characteristics of the processor over the last time period. It is assumed that the caller
maintains an internal count for determining the busy ratio of the logical processor (busy
ratio can be defined as the percentage of time the processor was busy executing
instructions and not idle). The caller then seeks to adjust the P-state for the next time
period to match the busy ratio from the previous time period. For example, if the busy
ratio for a given period was 100%, and the
performance_index
returned by
PAL_GET_PSTATE was 60, then this indicates that the P-state for the next time period
should be P0 (which has performance index of 100). The caller would then call the
PAL_SET_PSTATE procedure to transition the processor to the P0 state. In essence, if
the busy ratio is greater than the
performance_index
returned by PAL_GET_PSTATE, the
caller responds to the increased demand requirement of the workload by transitioning
the processor to a higher-performance P-state. Alternatively, if the busy ratio is lower
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...