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| author | Andrew Waterman <andrew@sifive.com> | 2018-11-27 16:01:21 -0800 |
|---|---|---|
| committer | Andrew Waterman <andrew@sifive.com> | 2018-11-27 16:01:21 -0800 |
| commit | 743f1409466fd4b09b5c77170bcbda0e2c47d8ee (patch) | |
| tree | e63805cad9f5c8e1200df5a55a066d2e6b6bdb86 | |
| parent | facb1705a4c27f9d9762bebd46fbd2f6ef08c5bb (diff) | |
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Add commentary about MPRV and writable XLEN
Closes #107
| -rw-r--r-- | src/machine.tex | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/machine.tex b/src/machine.tex index 2eb40f5..539838f 100644 --- a/src/machine.tex +++ b/src/machine.tex @@ -662,6 +662,11 @@ MXR allows instruction words to be loaded from pages marked execute-only. For simplicity, MPRV and MXR are in effect regardless of privilege mode, but in normal use will only be enabled for short sequences in machine mode. + +The current privilege mode and the privilege mode specified by MPP might have +different XLEN settings. When MPRV=1, load and store memory addresses are +treated as though the current XLEN were set to MPP's XLEN, following the rules +in Section~\ref{xlen-control}. \end{commentary} The SUM (permit Supervisor User Memory access) bit modifies the privilege with |