Messages in this thread |  | | Date | Sat, 13 Jun 2020 11:39:14 +0200 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH] x86/msr: Filter MSR writes |
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On Fri, Jun 12, 2020 at 10:39:35PM +0200, Peter Zijlstra wrote: > On Fri, Jun 12, 2020 at 07:48:01PM +0200, Borislav Petkov wrote: > > On Fri, Jun 12, 2020 at 10:20:03AM -0700, Linus Torvalds wrote: > > > Since you already added the filtering, this looks fairly sane. > > > > > > IOW, what MSR's do we expect people to maybe write to normally? You > > > added MSR_IA32_ENERGY_PERF_BIAS as an allowed MST, maybe there are > > > others? > > > > Right, this MSR is being written by cpupower in tools/. My search was > > confined within the kernel source only so there very likely are others. > > So that tool writing to /dev/msr has already caused pain; the direct > result is that the intel pstate driver doesn't want to use an MSR shadow > variable to avoid RDMSR because that'd loose input. > > https://lkml.org/lkml/2019/3/25/310 > > (sorry, that's what google found me) > > So ideally we'd just disallow it too. It already has a sysfs file (per > those patches): > > Documentation/admin-guide/pm/intel_epb.rst
Damn, that has fallen off my radar completely and the reason for me requesting the sysfs interface is the *same* - kill the direct MSR access.
Rafael, how about I refresh those patches and teach cpupower to access the sysfs interface too and we drop that MSR from the whitelist too?
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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