linux-kernel - Re: [PATCH 01/23] x86, kaiser: prepare assembly for entry/exit CR3 switching

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Message-ID: <alpine.DEB.2.20.1711012155000.1942@nanos>
Date:   Wed, 1 Nov 2017 22:01:28 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, luto@...nel.org,
        torvalds@...ux-foundation.org, keescook@...gle.com,
        hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 01/23] x86, kaiser: prepare assembly for entry/exit CR3
 switching

On Tue, 31 Oct 2017, Dave Hansen wrote:
>  
> +	pushq	%rdi
> +	SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi
> +	popq	%rdi

Can you please have a macro variant which does:

    SWITCH_TO_KERNEL_CR3_PUSH reg=%rdi

So the pushq/popq is inside the macro. This has two reasons:

   1) If KAISER=n the pointless pushq/popq go away

   2) We need a boottime switch for that stuff, so we better have all
      related code in the various macros in order to patch it in/out.

Also, please wrap these macros in #ifdef KAISER right away and provide the
stubs as well. It does not make sense to have them in patch 7 when patch 1
introduces them.

Aside of Boris comments this looks about right.

Thanks,

	tglx