Smhpm Extension
Versions
- 1.11.0
-
- State
-
ratified
- Ratification date
-
2019-12
- Changes
-
-
Defined the mcountinhibit CSR, which stops performance counters from incrementing to reduce energy consumption.
-
- 1.12.0
-
- State
-
ratified
- Ratification date
-
2021-12
- Changes
-
-
PMP changes require an SFENCE.VMA on any hart that implements page-based virtual memory, even if VM is not currently enabled.
-
PMP reset values are now platform-defined.
-
An additional 48 optional PMP registers have been defined.
-
- 1.13.0
-
- State
-
frozen
Parameters
This extension has the following implementation options:
- COUNTINHIBIT_EN
-
Type
array
Valid Values
32-element array where:
[0] is boolean
[1] is false
[2] is boolean
additional items are:
booleanDescription
Indicates which hardware performance monitor counters can be disabled from mcountinhibit.
An unimplemented counter cannot be specified, i.e., if HPM_COUNTER_EN[3] is false, it would be illegal to set COUNTINHIBIT_EN[3] to true.
COUNTINHIBIT_EN[1] can never be true, since it corresponds to mcountinhibit, which is always read-only-0.
COUNTINHIBIT_EN[3:31] must all be false if Zihpm is not implemented.
- HPM_COUNTER_EN
-
Type
array
Valid Values
32-element array where:
[0] is false
[1] is false
[2] is false
additional items are:
booleanDescription
List of HPM counters that are enabled. There is one entry for each hpmcounter.
The first three entries must be false (as they correspond to CY, IR, TM in, e.g.
mhmpcountinhibit) Index 3 in HPM_COUNTER_EN corresponds to hpmcounter3. Index 31 in HPM_COUNTER_EN corresponds to hpmcounter31. - HPM_EVENTS
-
Type
array
Valid Values
array of 58-bit integer
Description
List of defined event numbers that can be written into hpmeventN
- MCOUNTENABLE_EN
-
Type
array
Valid Values
32-element array of boolean
Description
Indicates which counters can be delegated via mcounteren.
An unimplemented counter cannot be specified, i.e., if HPM_COUNTER_EN[3] is false, it would be illegal to set MCOUNTENABLE_EN[3] to true.