medeleg

Machine Exception Delegation

Controls exception delegation from M-mode to (H)S-mode .

An exception cause is delegated to (H)S-mode when all of the following hold:

The corresponding field in medeleg is set.
The current privilege level is not M-mode.

Otherwise, an exception cause is handled by M-mode.

See interrupt documentation for more details.

Attributes

Defining Extension	S, version >= 0
CSR Address	0x302
Length	64-bit
Privilege Mode	M

Defining Extension

S, version >= 0

CSR Address

0x302

Length

64-bit

Privilege Mode

Format

Figure 1. medeleg format

Field Summary

Name Location Type Reset Value

Name	Location	Type	Reset Value
`IAM`	0	RW	UNDEFINED_LEGAL
`IAF`	1	RW	UNDEFINED_LEGAL
`II`	2	RW	UNDEFINED_LEGAL
xref:exts:B.adoc#B-def[B]	3	RW	UNDEFINED_LEGAL
`LAM`	4	RW	UNDEFINED_LEGAL
`LAF`	5	RW	UNDEFINED_LEGAL
`SAM`	6	RW	UNDEFINED_LEGAL
`SAF`	7	RW	UNDEFINED_LEGAL
`EU`	8	RW	UNDEFINED_LEGAL
`ES`	9	RW	UNDEFINED_LEGAL
`EVS`	10	RW	UNDEFINED_LEGAL
`EM`	11	RO	0
`IPF`	12	RW	UNDEFINED_LEGAL
`LPF`	13	RW	UNDEFINED_LEGAL
`SPF`	15	RW	UNDEFINED_LEGAL
`IGPF`	20	RW	UNDEFINED_LEGAL
`LGPF`	21	RW	UNDEFINED_LEGAL
`VI`	22	RW	UNDEFINED_LEGAL
`SGPF`	23	RW	UNDEFINED_LEGAL

IAM

UNDEFINED_LEGAL

IAF

UNDEFINED_LEGAL

II

UNDEFINED_LEGAL

xref:exts:B.adoc#B-def[B]

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

UNDEFINED_LEGAL

Fields

`IAM`

Location: 0
Description: Instruction Address Misaligned

Delegates Instruction Address Misaligned exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.IAM 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`IAF`

Location: 1
Description: Instruction Access Fault

Delegates Instruction Access Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.IAF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`II`

Location: 2
Description: Illegal Instruction

Delegates Illegal Instruction exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.II 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

B

Location: 3
Description: Breakpoint

Delegates Breakpoint exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.B 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`LAM`

Location: 4
Description: Load Address Misaligned

Delegates Load Address Misaligned exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

[when,"MISALIGNED_LDST == true"]
Note that because this implementation supports misaligned loads, this exception will never occur.
However, the writeable bit should be presented anyway.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.LAM 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`LAF`

Location: 5
Description: Load Access Fault

Delegates Load Access Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.LAF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`SAM`

Location: 6
Description: Store/AMO Address Misaligned

Delegates Store/AMO Address Misaligned exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

[when,"MISALIGNED_LDST == true && MISALIGNED_AMO == true"]
Note that beause the implementation supports misaligned stores and misaligned AMOs (or no AMOs), this exception will never occur.
Even so, the writeable bit should be presented anyway.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.SAM 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`SAF`

Location: 7
Description: Store/AMO Access Fault

Delegates Store/AMO Access Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.SAF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`EU`

Location: 8
Description: Environment Call from U-Mode

Delegates Environment Call from U-mode exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.EU 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`ES`

Location: 9
Description: Environment Call from S-Mode

Delegates Environment Call from S-mode exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.ES 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! (H)S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`EVS`

Location: 10
Description: Environment Call from VS-Mode

Delegates Environment Call from VS-mode exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.EVS 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! (H)S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`EM`

Location: 11
Description: Environment Call from M-Mode

An Environment Call from M-mode cannot be delegated, so this is a read-only field.

All Enviornment Call from M-mode exceptions are taken by M-mode.
Type: RO
Reset value: 0

`IPF`

Location: 12
Description: Instruction Page Fault

Delegates Instruction Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.IPF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`LPF`

Location: 13
Description: Load Page Fault

Delegates Load Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.LPF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`SPF`

Location: 15
Description: Store/AMO Page Fault

Delegates Store/AMO Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.LPF 2+^.>! Current Mode
.>h! M-mode .>h! S-mode

! 0 ! M ! M
! 1 ! M ! S
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`IGPF`

Location: 20
Description: Instruction Guest Page Fault

Delegates Instruction Guest Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.IGPF 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! HS
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`LGPF`

Location: 21
Description: Load Guest Page Fault

Delegates Load Guest Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.LGPF 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! HS
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`VI`

Location: 22
Description: Virtual Instruction

Delegates Virtual Instruction exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.VI 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! HS
!===
Type: RW
Reset value: UNDEFINED_LEGAL

`SGPF`

Location: 23
Description: Store/AMO Guest Page Fault

Delegates Store/AMO Guest Page Fault exceptions to (H)S-mode.

Exceptions are never taken into a less-privileged mode, regardless of medeleg.

The handling mode is determined as follows:

[separator="!",%autowidth, %footer]
!===
.2+! medeleg.SGPF 2+^.>! Current Mode
.>h! M-mode .>h! (H)S-mode

! 0 ! M ! M
! 1 ! M ! HS
!===
Type: RW
Reset value: UNDEFINED_LEGAL