senvcfg

Supervisor Environment Configuration

Contains fields that control certain characteristics of the U-mode execution environment.

Attributes

CSR Address

0x10a

Defining extension

  • allOf:

    • S, version >=1.12

    • U, version >= U@1.0.0

Length

64-bit

Privilege Mode

S

Format

senvcfg format
Figure 1. senvcfg format

Field Summary

Name Location Type Reset Value

CBZE

7

RW

UNDEFINED_LEGAL

CBCFE

6

RW

UNDEFINED_LEGAL

CBIE

5:4

RW-R

UNDEFINED_LEGAL

FIOM

0

RW

0

Fields

CBZE

Location

senvcfg[7]

Description

Cache Block Zero instruction Enable

Bit is read-only 0 when menvcfg.CBZE is clear.

Enables the execution of the cache block zero instruction, cbo.zero, in U-mode and (in conjunction with henvcfg.CBZE) VU-mode.

  • 0: The instruction raises an illegal instruction or virtual instruction exception

  • 1: The instruction is executed

    To summarize access:

menvcfg.CBZE

senvcfg.CBZE behavior +

0

read-only 0

1

writable, independent bit from menvcfg.CBZE

+ See cbo.zero for a summary of the effect.

Type

RW

Read-Write

Field is writable by software. Any value that fits in the field is acceptable and shall be retained for subsequent reads.
Reset value

UNDEFINED_LEGAL

CBCFE

Location

senvcfg[6]

Description

Cache Block Clean and Flush instruction Enable

Enables the execution of the cache block clean instruction, cbo.clean, and the cache block flush instruction, cbo.flush, in S-mode .

  • 0: The instruction raises an illegal instruction or virtual instruction exception

  • 1: The instruction is executed

    To summarize access:

menvcfg.CBCFE

senvcfg.CBCFE behavior +

0

read-only 0

1

writable, independent bit from menvcfg.CBCFE

+ See cbo.clean and/or cbo.flush for a summary of the effect.

Type

RW

Read-Write

Field is writable by software. Any value that fits in the field is acceptable and shall be retained for subsequent reads.
Reset value

UNDEFINED_LEGAL

CBIE

Location

senvcfg[5:4]

Description

Cache Block Invalidate instruction Enable

This field has restricted values based on the value of menvcfg.CBIE. When an invalid value is written, it is ignored and the field remains unchanged.

menvcfg.CBIE

Valid values of senvcfg.CBIE +

00

00

01

00, 01

11

00, 01, 11

Controls execution of the cache block invalidate instruction, cbo.inval, in U-mode and VU-mode (together with henvcfg.CBIE) .

  • 00: The instruction raises an illegal instruction or virtual instruction exception

  • 01: The instruction is executed and performs a flush operation

  • 10: Reserved

  • 11: The instruction is executed and performs an invalidate operation

    See cbo.inval for more details.

Type

RW-R

Read-Write Restricted

Field is writable by software. Only certain values are legal. Writing an illegal value into the field is ignored, and the field retains its prior state.
Reset value

UNDEFINED_LEGAL

Software write

This field has special behavior when written by software (e.g., through csrrw).

When software tries to write csr_value, the field will be written with the return value of the function below.

if (csr_value.CBIE == 0 || csr_value.CBIE == 1 || csr_value.CBIE == 3) {
  return csr_value.CBIE;
} else {
  return UNDEFINED_LEGAL_DETERMINISTIC;
}

FIOM

Location

senvcfg[0]

Description

Fence of I/O implies Memory

When either senvcfg.FIOM or menvcfg.FIOM is set, FENCE instructions ordering I/O regions also implicitly order memory regions when executed in U-mode as follows:

Instruction bit Meaning when set

PI
PO

Predecessor device input and memory reads (PR implied)
Predecessor device output and memory writes (PW implied)

SI
SO

Successor device input and memory reads (SR implied)
Successor device output and memory writes (SW implied)

Similarly, in U-mode when FIOM=1, if an atomic instruction that accesses a region ordered as device I/O has its aq and/or rl bit set, then that instruction is ordered as though it accesses both device I/O and memory.

See fence for more details.

Type

RW

Read-Write

Field is writable by software. Any value that fits in the field is acceptable and shall be retained for subsequent reads.
Reset value

0