htval

Hypervisor Trap Value Register

When a trap is taken into HS-mode, htval is written with additional exception-specific information, alongside stval, to assist software in handling the trap.

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

A guest-page fault may arise due to an implicit memory access during first-stage (VS-stage) address translation, in which case a guest physical address written to htval is that of the implicit memory access that faulted-for example, the address of a VS-level page table entry that could not be read. (The guest physical address corresponding to the original virtual address is unknown when VS-stage translation fails to complete.) Additional information is provided in CSR htinst to disambiguate such situations.

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

htval 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

Defining Extension	H, version >= 0
CSR Address	0x643
Length	32 when CSR[misa].MXL == 0 64 when CSR[misa].MXL == 1
Privilege Mode	M

Defining Extension

H, version >= 0

CSR Address

0x643

Length

32 when CSR[misa].MXL == 0 64 when CSR[misa].MXL == 1

Privilege Mode

Format

This CSR format changes dynamically.

Figure 1. htval Format when CSR[misa].MXL == 0

Figure 2. htval Format when CSR[misa].MXL == 1

Field Summary

Name	Location	Type	Reset Value
htval.VALUE	* 31:0 when CSR[misa].MXL == 0 * 63:0 when CSR[misa].MXL == 1	[when,"(((REPORT_GPA_IN_TVAL_ON_LOAD_GUEST_PAGE_FAULT \|\| REPORT_GPA_IN_TVAL_ON_STORE_AMO_GUEST_PAGE_FAULT) \|\| REPORT_GPA_IN_TVAL_ON_INSTRUCTION_GUEST_PAGE_FAULT) \|\| REPORT_GPA_IN_TVAL_ON_INTERMEDIATE_GUEST_PAGE_FAULT)"] RW-H [when,"!(((REPORT_GPA_IN_TVAL_ON_LOAD_GUEST_PAGE_FAULT \|\| REPORT_GPA_IN_TVAL_ON_STORE_AMO_GUEST_PAGE_FAULT) \|\| REPORT_GPA_IN_TVAL_ON_INSTRUCTION_GUEST_PAGE_FAULT) \|\| REPORT_GPA_IN_TVAL_ON_INTERMEDIATE_GUEST_PAGE_FAULT)"] RO	UNDEFINED_LEGAL

Name

Location

Type

Reset Value

htval.VALUE

* 31:0 when CSR[misa].MXL == 0 * 63:0 when CSR[misa].MXL == 1

[when,"(((REPORT_GPA_IN_TVAL_ON_LOAD_GUEST_PAGE_FAULT || REPORT_GPA_IN_TVAL_ON_STORE_AMO_GUEST_PAGE_FAULT) || REPORT_GPA_IN_TVAL_ON_INSTRUCTION_GUEST_PAGE_FAULT) || REPORT_GPA_IN_TVAL_ON_INTERMEDIATE_GUEST_PAGE_FAULT)"] RW-H [when,"!(((REPORT_GPA_IN_TVAL_ON_LOAD_GUEST_PAGE_FAULT || REPORT_GPA_IN_TVAL_ON_STORE_AMO_GUEST_PAGE_FAULT) || REPORT_GPA_IN_TVAL_ON_INSTRUCTION_GUEST_PAGE_FAULT) || REPORT_GPA_IN_TVAL_ON_INTERMEDIATE_GUEST_PAGE_FAULT)"] RO

UNDEFINED_LEGAL

Fields

`VALUE`

Location

31:0 when CSR[misa].MXL == 0
63:0 when CSR[misa].MXL == 1

Description

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

Type

RW-H

Reset value: UNDEFINED_LEGAL