linux-kernel - Re: [PATCH v3 2/5] x86/microcode/intel: Allow a late-load only if a min rev is specified

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Message-ID: <YwaBim3Xt3Il3KXm@zn.tnic>
Date:   Wed, 24 Aug 2022 21:52:42 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ashok Raj <ashok.raj@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        LKML Mailing List <linux-kernel@...r.kernel.org>,
        X86-kernel <x86@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Tom Lendacky <thomas.lendacky@....com>,
        Jacon Jun Pan <jacob.jun.pan@...el.com>
Subject: Re: [PATCH v3 2/5] x86/microcode/intel: Allow a late-load only if a
 min rev is specified

On Tue, Aug 23, 2022 at 12:08:27AM +0000, Ashok Raj wrote:
> Correct, but print_err parameter is 0 when called from scan_microcode() and 1
> when called from generic_load_microcode().

Well, scan_microcode() gets called from save_microcode_in_initrd() which
is fs_initcall and if we had to be really precise, print_err being 0
there is wrong.

Because at fs_initcall time we can very well print error messages. But
that print_err thing is an old relic so will have to get fixed some
other day.

> We do min_rev enforcement only when print_err is set.

That's wrong - you need to do min_rev enforcement only when you're
loading microcode late. I.e., to paste from my previous mail:

"So you'd have to pass down the fact that you're doing late loading from
request_microcode_fw().

Now, I'm staring at that ugly refresh_fw bool arg in that function and
I *think* I did it 10 years ago because it shouldn't try to load from
the fs when it is resuming because there might not be a fs yet... or
something to that effect.

tglx might have a better idea how to check we're in the ->starting
notifier..."

IOW, we're going to have to do something like

->request_microcode_fw(, ... late_loading=true)

and I wanted to reuse that refresh_fw arg instead of adding another
one...

HTH.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette