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

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Message-ID: <20230225172832.sqdd7dejkkmjxpt6@treble>
Date:   Sat, 25 Feb 2023 09:28:32 -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 Sat, Feb 25, 2023 at 01:21:49PM +0100, Borislav Petkov wrote:
> On Fri, Feb 24, 2023 at 05:32:02PM -0800, Josh Poimboeuf wrote:
> > > Is it intended to be set regardless of the spectre_v2 mitigation status?
> > 
> > Right, it needs to check spectre_v2_enabled.
> 
> Right, I realized this too this morning, while sleeping, so I made me
> a note on the nightstand to fix it... :-)
> 
> > Also, this code might be a better fit in identify_secondary_cpu() with
> > the other MSR-writing bug-related code.
> 
> Same path:
> 
> identify_secondary_cpu->identify_cpu->this_cpu->c_init(c)->init_amd
> 
> Plus, it keeps the vendor code where it belongs.

All the other "bug" code in identify_secondary_cpu() *is*
vendor-specific.

And for that matter, so is most of the code in bugs.c.

I'm thinking we should just move all this MSR-writing bug-related code
into a new cpu_init_bugs() function in bugs.c which can be called by
identify_secondary_cpu().

Then we have more "bug" code together and all the local
variables/functions like spectre_v2_in_ibrs_mode() can remain local.

-- 
Josh