linux-kernel - Re: [PATCH v2 1/7] x86/paravirt: Make read_cr2() CALLEE

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Message-ID: <CALCETrUJeOPvujnx--ZLQXJAaj0x8YEjftdt-rR=UiVijCrvcg@mail.gmail.com>
Date:   Thu, 4 Jul 2019 14:49:27 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        He Zhe <zhe.he@...driver.com>,
        Joel Fernandes <joel@...lfernandes.org>, devel@...ukata.com
Subject: Re: [PATCH v2 1/7] x86/paravirt: Make read_cr2() CALLEE_SAVE

On Thu, Jul 4, 2019 at 1:03 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> The one paravirt read_cr2() implementation (Xen) is actually quite
> trivial and doesn't need to clobber anything other than the return
> register. By making read_cr2() CALLEE_SAVE we avoid all the PUSH/POP
> nonsense and allow more convenient use from assembly.

Wow, this is incomprehensible! :)  I'll trust Juergen's review.

--Andy