linux-kernel - Re: [PATCH] x86/CPU/AMD: Make sure EFER[AIBRSE] is set

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Message-ID: <20230226172726.iidbgidy5336npi4@treble>
Date:   Sun, 26 Feb 2023 09:27:26 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Kim Phillips <kim.phillips@....com>, x86@...nel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Alexey Kardashevskiy <aik@....com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/CPU/AMD: Make sure EFER[AIBRSE] is set

On Sun, Feb 26, 2023 at 12:18:06PM +0100, Borislav Petkov wrote:
> > Right, so rather than spreading all the bug-related MSR logic around,
> > just do it in one spot.
> 
> It is all CPU init code and I'm wondering if splitting stuff by vendor
> wouldn't make all that maze in bugs.c a lot more palatable. And get rid
> of
> 
> $ git grep VENDOR arch/x86/kernel/cpu/bugs.c | wc -l
> 11
> 
> those, for starters.
> 
> There's this trade-off of
> 
> 1. keeping bugs setup code in one place - but then you need to do vendor
>    checks and the other CPU setup code is somewhere else and it is
>    probably related, MSR_AMD64_DE_CFG_LFENCE_SERIALIZE_BIT in amd.c for
>    example.
> 
> or
> 
> 2. separating it into their respective files. Then the respective vendor
>    code is simple because you don't need vendor checks. It would need to
>    be done in a slick way, though, so that it remains maintainable.

At least now it's a (mostly) self-contained hornets nest.  I'm not sure
we want to poke it :-)

And I'm not sure spreading the mess around would be an improvement.

-- 
Josh