Something is stopping me from writing MSRs (0x150 / Undervolting to be exact)

[Dylanger Daly]

Hey Guys,

I'm not able to undervolt my laptop because I can't seem to write to the MSR 0x150 (Voltage Offset).

I _think_ it's because Xen dosen't allow wrmsr in dom0 to actually write anything.

I think wrmsr should be available to dom0, but not other appVMs.

Does anyone know what could be blocking dom0 from writing MSRs?

Cheers!

[Dylanger Daly]

For anyone wondering I've managed to enable Undervolting Intel CPUs on Qubes: https://github.com/QubesOS/qubes-vmm-xen/pull/55/commits/0a64e97df34a352366787bbd19ff27f5dba6e13a

I'm trying to get it merged into Xen, however the process is convoluted to say the least, in any case, if you want to use it, review the patches and apply to `vmm-xen`

[Marek Marczykowski-Górecki]

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On Wed, Apr 17, 2019 at 11:57:12PM -0700, Dylanger Daly wrote:
> I'm trying to get it merged into Xen, however the process is convoluted to say the least, in any case, if you want to use it, review the patches and apply to `vmm-xen`

Simplified process, including git setup:

# setup git
git config --global user.name "your name" # fill this
git config --global user.email "your email" # fill this

# download xen
git clone git://xenbits.xenproject.org/xen.git
cd xen

# apply your patch

git checkout -b msr-patch
git apply <path to the patch you've already made>
git commit -s
# fill commit message

# And then you can use git for sending the patch:

git config --global sendemail.from "YOUR NAME <us...@example.org>"
git config --global sendemail.smtpserver smtp.example.org
git config --global sendemail.smtpuser USER
# depending on your config you may also set:
git config --global sendemail.smtpencryption tls

git config sendemail.ccCmd "$PWD/scripts/get_maintainer.pl"
# send one patch on the top
git send-email --to=xen-...@lists.xenproject.org -1

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[Dylanger Daly]

Thank you!
```
Send this email? ([y]es|[n]o|[e]dit|[q]uit|[a]ll): yes
OK. Log says:
```
I managed to send it just now