From: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
To: Andi Kleen <andi@firstfloor.org>
Cc: peterz@infradead.org, x86@kernel.org, eranian@google.com,
kan.liang@intel.com, linux-kernel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions
Date: Thu, 11 Oct 2018 08:43:27 -0300 [thread overview]
Message-ID: <20181011114327.oo3at77hxucpfaon@khazad-dum.debian.net> (raw)
In-Reply-To: <20181010162608.23899-1-andi@firstfloor.org>
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
next prev parent reply other threads:[~2018-10-11 11:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 16:26 [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions Andi Kleen
2018-10-10 16:26 ` [PATCH v2 2/2] perf/x86/kvm: Avoid unnecessary work in guest filtering Andi Kleen
2018-10-10 16:37 ` [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions Borislav Petkov
2018-10-11 11:43 ` Henrique de Moraes Holschuh [this message]
2018-10-17 9:59 ` Thomas Gleixner
2018-10-19 23:47 ` Andi Kleen
2018-10-20 8:19 ` Thomas Gleixner
2018-10-20 14:38 ` Andi Kleen
2018-10-21 10:20 ` Thomas Gleixner
2018-10-21 15:13 ` Borislav Petkov
2018-10-25 23:23 ` Andi Kleen
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