linux-kernel - Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed

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Date:   Tue, 27 Sep 2022 12:10:50 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace
 mtrr_aps_delayed_init

On Tue, Sep 27, 2022 at 10:57:37AM +0200, Juergen Gross wrote:
> TBH I don't see the point of having an accessor which is just setting a
> variable to "true". But if you like it better, I can keep it.

Accessors are always better, no matter how silly. :)

But, in trying to grok your next patch - you really should split those
more complex ones because they're a pain to review - I'm starting to
wonder whether we could even remove mtrr_aps_delayed_init and make the
delayed init the default.

Because, AFAICT, set_mtrr_aps_delayed_init() is called by default
by native_smp_prepare_cpus(). Which is called by hyperv and
arch/x86/xen/smp_hvm.c.

The only one that's not calling it is arch/x86/xen/smp_pv.c but that
thing doesn't support MTRRs in the first place, right?

Which means, it doesn't need delayed MTRR init anyway.

Which would then mean that this would simplify this ugly logic even more.

Or am I missing an angle?

It is possible in this nuts code.

Thx.

-- 
Regards/Gruss,
    Boris.

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