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| author | Andrew Waterman <andrew@sifive.com> | 2024-02-20 18:07:55 -0800 |
|---|---|---|
| committer | Andrew Waterman <andrew@sifive.com> | 2024-02-29 15:39:17 -0800 |
| commit | 10700d0766501c9a4ce16c7cab53c908c44d5158 (patch) | |
| tree | aaa3715d879802bb47e89e72f06cf5d3899e7aaf /src/rnmi.adoc | |
| parent | 98918c844281332f4e75ad7d4c818ad9ecaeb5ad (diff) | |
| download | riscv-isa-manual-10700d0766501c9a4ce16c7cab53c908c44d5158.zip riscv-isa-manual-10700d0766501c9a4ce16c7cab53c908c44d5158.tar.gz riscv-isa-manual-10700d0766501c9a4ce16c7cab53c908c44d5158.tar.bz2 | |
Update Smrnmi to account for Smdbltrp extension
This is a backwards compatible change to support resumable double
traps within M-mode when both extensions are implemented. Although
the resumability feature is not terribly interesting, the reuse of
the Smrnmi state for M-mode double traps aids debugging (and fault
diagnosis for the hardware-error exception case).
Diffstat (limited to 'src/rnmi.adoc')
| -rw-r--r-- | src/rnmi.adoc | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/src/rnmi.adoc b/src/rnmi.adoc index 9938917..cbd19da 100644 --- a/src/rnmi.adoc +++ b/src/rnmi.adoc @@ -71,9 +71,15 @@ of holding. .Resumable NMI cause `mncause`. include::images/bytefield/mncause.edn[] -The `mncause` CSR holds the reason for the NMI, with bit MXLEN-1 set to -1, and the NMI cause encoded in the least-significant bits or zero if -NMI causes are not supported. +The `mncause` CSR holds the reason for the NMI. +If the reason is an interrupt, bit MXLEN-1 is set to 1, and the NMI +cause is encoded in the least-significant bits. +If the reason is an interrupt and NMI causes are not supported, bit MXLEN-1 is +set to 1, and zero is written to the least-significant bits. +If the reason is an exception within M-mode that results in a double trap as +specified in the Smdbltrp extension, bit MXLEN-1 is set to 0 and the +least-significant bits are set to the cause code corresponding to the +exception that precipitated the double trap. .Resumable NMI status register `mnstatus`. include::images/bytefield/mnstatus.edn[] |