RE: [RFC PATCH 3/3] x86/microcode: Taint and warn on late loading

From: "Luck, Tony" <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>, Peter Zijlstra <peterz@infradead.org>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 3/3] x86/microcode: Taint and warn on late loading
Date: Wed, 25 May 2022 14:50:59 +0000	[thread overview]
Message-ID: <4644ff0530ba40948ed1f0e2e45a24d8@intel.com> (raw)
In-Reply-To: <Yo3cpb1yZhwhHEga@zn.tnic>

>> Then use early loading. There's too many fails associated with late
>> loading.
>
> Yes, short of
>
> TAINT_YOU_DID_SOMETHING_DANGEROUS
>
> we simply don't have a better taint flag.

Are taint flags in such short supply that you couldn't create a new one?

The OUT_OF_SPEC one already seems to be used in some dubious
ways:
1) Command line argument to clear a X86_FEATURES bit
2) Forcing PAE
3) Writing to an MSR not on the "approved" list

As you add more ways to set this taint bit, it becomes less useful
for debugging ... since now you have to dig into which of the possible
cases set the bit to decide whether it might have contributed to the
OOPS.

-Tony