linux-kernel - Re: Is GET_CR0_INTO

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Message-ID: <alpine.DEB.2.20.1710032139040.2278@nanos>
Date:   Tue, 3 Oct 2017 21:41:13 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Denys Vlasenko <dvlasenk@...hat.com>
cc:     Andy Lutomirski <luto@...nel.org>,
        Andy Lutomirski <luto@...capital.net>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: Is GET_CR0_INTO_EAX macro unused?

On Mon, 2 Oct 2017, Denys Vlasenko wrote:

> Hi Andy,
> 
> From by git archaeology, looks like last use of GET_CR0_INTO_EAX
> was removed long ago, in 2008 (see commit below).
> 
> Right now, I only grep it here in a comment in entry_32.S:
> /*
>  * We use macros for low-level operations which need to be overridden
>  * for paravirtualization.  The following will never clobber any registers:
>  *   INTERRUPT_RETURN (aka. "iret")
>  *   GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
> 
> To support GET_CR0_INTO_EAX, paravirt has PV_CPU_read_cr0 a.k.a.
> struct pv_cpu_ops::read_cr0 and a bunch of code to support it
> for each hypervisor.
> 
> Can we delete it?
> Or am I missing a non-obvious place where this macro is still in use?

That thing was simply forgotten and bitrots happily since 2008.

Thanks,

	tglx