Messages in this thread | | | Date | Thu, 11 Oct 2018 08:43:27 -0300 | From | Henrique de Moraes Holschuh <> | Subject | Re: [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions |
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On Wed, 10 Oct 2018, Andi Kleen wrote: > v2: > Remove all CPU match, only check boot cpu
IMHO, since it looks like a v3 will be necessary anyway, it could benefit from a comment reminding people about how to use it on older systems where "mixed CPU stepping" configurations were common.
This is *not* a relevant limitation, and it is easy enough to handle. But people writing quirks for very old Intel Xeon CPUs *today* (unlikely as that might be) might well forget the mixed-stepping gotcha...
Note that while mixed-stepping SMP configurations are *not* current practice, they *were* reasonably common practice more than a decade ago, officially supported both by Intel (there are Intel documents detailing the valid stepping combinations) and the server vendors.
Suggestion below.
> +/* > + * Match specific microcodes > + * > + * vendor/family/model/stepping must be all set. > + * min_ucode is optional and can be 0.
* only checks against the boot cpu. When mixed-stepping configs are valid for a CPU model, add a quirk for every valid stepping and do the fine-tuning in the quirk handler.
-- Henrique Holschuh
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