msr

Overview ¶

msr -- read and write MSRs with regular command or Forth

Synopsis:

msr [OPTIONS] r glob MSR
msr [OPTIONS] w glob MSR value
msr [OPTIONS] forth-word [forth-word ...]

Description:

This program reads and writes sets of MSRs, while allowing
them to by changed on a core by core or collective basis.

To read the msrs for 0 (sorry, the command is msr and the forth command
is msr, making this a bit confusing):
sudo msr 0 0x3a rd
Breaking that down:
0 - for cpu 0
0x3a - for register 0x3a
rd - pop a 32-bit int and a []string and use them to read 1 or more MSRs

for all:
sudo msr "'*" 0x3a rd

The "'" is needed to quote the * so forth does not think we're multiplying.

There are two convenience words so you can see how things break down.
You do not need them but they can help debug.
The above can also be written as
sudo msr "'*" cpu 0x3a reg rd

Here is a breakdown, running msr with each command in turn:
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ ./msr 0
0
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ ./msr 0 cpu
[/dev/cpu/0/msr]
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ ./msr 0 msr 0x3a
[[/dev/cpu/0/msr] 0x3a]
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ ./msr 0 msr 0x3a reg
[[/dev/cpu/0/msr] 58]
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ ./msr 0 cpu 0x3a reg rd
[0]
rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$

the typeof word adds more information.
$ sudo ./msr 0 cpu
0
$ sudo ./msr 0 cpu typeof
msr.CPUs
$ sudo ./msr 0 cpu 0x3a
[0 0x3a]
$ sudo ./msr 0 cpu 0x3a reg
[0 0x3a]
$ sudo ./msr 0 cpu 0x3a reg typeof
[0 msr.MSR]
$ sudo ./msr 0 cpu 0x3a reg rd
[0 0x3a [5]]
$

To read, then write all of them
sudo msr 0 0x3a rd 1 or wr
to just write them

Also, note, all the types are checked by assertions. The reg has to be
32 bits, the val 64

more examples:
read reg 0x3a and leave the list of MSRs and values on TOS, to be
printed at exit.

sudo msr "'"* 0x3a rd
[[/dev/cpu/0/msr /dev/cpu/1/msr /dev/cpu/2/msr /dev/cpu/3/msr] [5 5 5 5]]

From there, the write is easy:
sudo msr "'"* 0x3a rd wr

For convenience, we maintain the old read and write commands:
msr r <glob> <register>
msr w <glob> <register> <value>

Yep, it's a bit inconvenient; the idea is that in the simple case,
you will use the r and w commands. For programmatic cases, you can
work to build up a working set of arguments.

For example, I started with
msr "'"* cpu
and, once I saw the MSR selection was OK, built the command up from
there. At each step I could see the stack and whether I was going the
right direction.

The old commands remain: rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ sudo ./msr r 0 0x3a [5] rminnich@xcpu:~/gopath/src/github.com/u-root/u-root/cmds/core/msr$ sudo ./msr w 0 0x3a 5 [5]

For a view of what Forth is doing, run with -d.

msr reads and writes msrs using a Forth interpreter on argv

Synopsis:

To see what is available:
msr words

Description:

msr provides a set of Forth words that let you manage MSRs.
You can add new ones of your own.
If you are going to use forth, the general pattern of arguments
looks something like this:
msr <glob pattern> cpu <msr-number> msr <opcode>
e.g.,
msr '*' 0x3a rd
Will read the 3a msr on all CPUs.
The two first items will remain at TOS. They are implicitly converted to
msr.CPUs and msr.MSR when used. You can show how the will be converted with
the cpu and reg works.
You can build up the expressions bit by bit:
For a start, it provides some pre-defined words for well-known MSRs

push a [] of MSR names and the 0x3a register on the stack
IA32_FEATURE_CONTROL -- equivalent to * cpu 0x3a msr
The next two commands use IA32_FEATURE_CONTROL:
READ_IA32_FEATURE_CONTROL -- equivalent to IA32_FEATURE_CONTROL rd
LOCK IA32_FEATURE_CONTROL -- equivalent to IA32_FEATURE_CONTROL rd IA32_FEATURE_CONTROL 1 u64 or wr
e.g.

./msr IA32_FEATURE_CONTROL [[/dev/cpu/0/msr /dev/cpu/1/msr /dev/cpu/2/msr /dev/cpu/3/msr] 58]

As a special convenience, we have two useful cases:
r glob register -- read the MSR 'register' from cores matching 'glob'
w glob register value -- write the value to 'register' on all cores matching 'glob'

Examples (NOTE: single ', since it is a forth literal! '* NOT '*'):

Show the IA32 feature MSR on all cores
sudo msr READ_IA32_FEATURE_CONTROL
[[5 5 5 5]]
lock the registers
sudo msr LOCK_IA32_FEATURE_CONTROL
Just see it one core 0 and 1
sudo ./msr '[01]' 0x3a rd
[[5 5]]
Debug your cpu mask
sudo ./msr "'1*" "cpu"
1,10-19
Debug your command stack
sudo ./msr "'[01]" cpu 0x3a reg
[0-1 0x3a]

For rd, if you want to see it in hex (which should be the default
but it's complicated
sudo ./msr "'[01]" cpu 0x10 reg rd %#x printf
[0xf41c40e682bb8 0xf41c40e69876b]