Messages in this thread | | | Subject | Re: [PATCH] x86/msr: do not warn on writes to OC_MAILBOX | From | Srinivas Pandruvada <> | Date | Tue, 08 Sep 2020 18:02:05 -0700 |
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On Tue, 2020-09-08 at 21:30 +0200, Borislav Petkov wrote: > On Tue, Sep 08, 2020 at 12:18:38PM -0700, Sultan Alsawaf wrote: > > I'd like to point out that on Intel's recent 14nm parts, > > undervolting > > is not so much for squeezing every last drop of performance out of > > the > > SoC as it is for necessity. > > <snip interesting examples> > > Sounds to me that this undervolting functionality should be part of > the kernel and happen automatically. I have no clue, though, whether > people who do it, just get lucky and undervolting doesn't cause any > other hardware issues, or there's a real reason for this power > madness > and if not done, power-related failures happen only on some boxes so > they decided to do them on all. > > Or maybe BIOS is nuts, which is not a stretch. > The whole OC is based on experiments to come to correct values. This depends on whole system design not just CPUs. https://www.intel.com/content/www/us/en/gaming/resources/how-to-overclock.html It warns about system stability.
> Srinivas, what's the story here? I checked and there is no public spec. There are several mailbox commands with version dependent on the processor.
The actual OC mailbox implementation itself is implemented in Linux in intel_turbo_max_3 driver. So that is public. So someone can develop a driver and provide some sysfs to send mailbox commands, but kernel can't validate commands which can cause any security or stability issues. Not sure if this is acceptable standard. I don't think there is any precedent of creating such blind sysfs entries.
Thanks, Srinivas
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