linux-kernel - Re: [PATCH v2 07/12] x86: add new features for paravirt patching

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Message-ID: <20201209120307.GB18203@zn.tnic>
Date:   Wed, 9 Dec 2020 13:03:07 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jürgen Groß <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        luto@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 07/12] x86: add new features for paravirt patching

On Wed, Dec 09, 2020 at 08:30:53AM +0100, Jürgen Groß wrote:
> Hey, I already suggested to use ~FEATURE for that purpose (see
> https://lore.kernel.org/lkml/f105a63d-6b51-3afb-83e0-e899ea40813e@suse.com/

Great minds think alike!

:-P

> I'd rather make the syntax:
> 
> ALTERNATIVE_TERNARY <initial-code> <feature> <code-for-feature-set>
>                                              <code-for-feature-unset>
> 
> as this ...

Sure, that is ok too.

> ... would match perfectly to this interpretation.

Yap.

> Hmm, using flags is an alternative (pun intended :-) ).

LOL!

Btw, pls do check how much the vmlinux size of an allyesconfig grows
with this as we will be adding a byte per patch site. Not that it would
matter too much - the flags are a long way a comin'. :-)

> No, this is needed for non-Xen cases, too (especially pv spinlocks).

I see.

> > Can you give an example here pls why the paravirt patching needs to run
> > first?
> 
> Okay.

I meant an example for me to have a look at. :)

If possible pls.

Thx.

-- 
Regards/Gruss,
    Boris.

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