Messages in this thread |  | | Date | Sat, 6 Oct 2018 11:15:07 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH v1 1/2] x86/cpufeature: Add facility to match microcode revisions |
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On Sat, Oct 06, 2018 at 04:14:54PM +0200, Thomas Gleixner wrote: > On Fri, 5 Oct 2018, Andi Kleen wrote: > > +/* > > + * Match specific microcodes or steppings. > > What means microcodes or steppings? If you mean microcode revisions then > please spell it out and use it all over the place. steppings is confusing > at best as its associated to the CPU stepping.
The matcher can be used to match specific hardware steppings by setting the min/max_ucode to 0 or specific microcode revisions (which are associated with steppings)
> > +const struct x86_ucode_id *x86_match_ucode_all(const struct x86_ucode_id *match) > > Can you please name that so it's obvious that this checks all cpus, but > aside of that, why would a system ever end up with different microcode > revisions at all? The changelog is not mentioning any reason for this > function and "/* Check all CPUs */" is not helpful either.
We still support the old microcode interface that allows updates per CPU, and also it could happen during CPU hotplug.
> > > + int cpu; > > + const struct x86_ucode_id *all_m = NULL; > > + bool first = true; > > + > > + for_each_online_cpu(cpu) { > > What guarantees that CPUs cannot be plugged? You either need to have > cpus_read_lock() in this function or a lockdep_assert_cpus_held().
In my case the caller, but yes should be documented.
-Andi
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