| .. SPDX-License-Identifier: GPL-2.0+ |
| |
| .. index:: |
| single: msr (command) |
| |
| msr command |
| =========== |
| |
| Synopsis |
| -------- |
| |
| :: |
| |
| msr read <op> |
| msr write <op> <hi> <lo> |
| |
| Description |
| ----------- |
| |
| The msr command reads and writes machine-status registers (MSRs) on x86 CPUs. |
| The information is a 64-bit value split into two parts, <hi> for the top 32 |
| bits and <lo> for the bottom 32 bits. |
| |
| The operation <op> selects what information is read or written. |
| |
| msr read |
| ~~~~~~~~ |
| |
| This reads an MSR and displays the value obtained. |
| |
| msr write |
| ~~~~~~~~~ |
| |
| This writes a value to an MSR. |
| |
| Configuration |
| ------------- |
| |
| The msr command is only available on x86. |
| |
| Return value |
| ------------ |
| |
| The return value $? is 0 (true). |
| |
| Example |
| ------- |
| |
| This shows reading msr 0x194 which is MSR_FLEX_RATIO on Intel CPUs:: |
| |
| => msr read 194 |
| 00000000 00011200 # Bits 16 (flex ratio enable) and 20 (lock) are set |
| |
| This shows adjusting the energy-performance bias on an Intel CPU:: |
| |
| => msr read 1b0 |
| 00000000 00000006 # 6 means 'normal' |
| |
| => msr write 1b0 0 f # change to power-save |
| => msr read 1b0 |
| 00000000 0000000f |