mtval2

Machine Second Trap Value Register

When a trap is taken into M-mode from a virtual mode, mtval2 is written with additional exception-specific information, alongside mtval, to assist software in handling the trap.

When a guest-page-fault trap is taken into M-mode, mtval2 is written with either zero or the guest physical address that faulted, shifted right by 2 bits. For other traps, mtval2 is set to zero, but a future standard or extension may redefine mtval2’s setting for other traps.

If a guest-page fault is due to an implicit memory access during first-stage (VS-stage) address translation, a guest physical address written to mtval2 is that of the implicit memory access that faulted. Additional information is provided in CSR mtinst to disambiguate such situations.

Otherwise, for misaligned loads and stores that cause guest-page faults, a nonzero guest physical address in mtval2 corresponds to the faulting portion of the access as indicated by the virtual address in mtval. For instruction guest-page faults on systems with variable-length instructions, a nonzero mtval2 corresponds to the faulting portion of the instruction as indicated by the virtual address in mtval.

mtval2 is a WARL register that must be able to hold zero and may be capable of holding only an arbitrary subset of other 2-bit-shifted guest physical addresses, if any.

Attributes

CSR Address

0x34b

Defining extension

  • H, version >= 0

Length

64-bit

Privilege Mode

M

Format

mtval2 format
Figure 1. mtval2 format

Field Summary

Name Location Type Reset Value

VALUE

63:0

RW-H

UNDEFINED_LEGAL

Fields

VALUE

Location

mtval2[63:0]

Description

Exception-specific information for a trap into M-mode.

Type

RW-H

Read-Write with Hardware update

Field is writable by software. Any value that fits in the field is acceptable. Hardware also updates the field without an explicit software write.

Reset value

UNDEFINED_LEGAL