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Date: Fri, 17 Nov 2017 19:07:13 +0100
From: Borislav Petkov <bp@alien8.de>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
        Juergen Gross <jgross@suse.com>, Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>, Mike Galbraith <efault@gmx.de>,
        Chris Wright <chrisw@sous-sol.org>, Alok Kataria <akataria@vmware.com>,
        Rusty Russell <rusty@rustcorp.com.au>,
        virtualization@lists.linux-foundation.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        xen-devel@lists.xenproject.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 03/13] x86/paravirt: Convert native patch assembly code
 strings to macros
Message-ID: <20171117180713.e4up3dwrszpatka6@pd.tnic>
References: <cover.1507128293.git.jpoimboe@redhat.com>
 <e4cea2b8aa8ca23122d9c807784ca62ee6cbbff8.1507128293.git.jpoimboe@redhat.com>
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On Wed, Oct 04, 2017 at 10:58:24AM -0500, Josh Poimboeuf wrote:
> Convert the hard-coded native patch assembly code strings to macros to
> facilitate sharing common code between 32-bit and 64-bit.
> 
> These macros will also be used by a future patch which requires the GCC
> extended asm syntax of two '%' characters instead of one when specifying
> a register name.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
>  arch/x86/include/asm/special_insns.h | 24 ++++++++++++++++++++++++
>  arch/x86/kernel/paravirt_patch_32.c  | 21 +++++++++++----------
>  arch/x86/kernel/paravirt_patch_64.c  | 29 +++++++++++++++--------------
>  3 files changed, 50 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
> index ac402c6fc24b..0549c5f2c1b3 100644
> --- a/arch/x86/include/asm/special_insns.h
> +++ b/arch/x86/include/asm/special_insns.h
> @@ -6,6 +6,30 @@
>  
>  #include <asm/nops.h>
>  
> +#ifdef CONFIG_X86_64
> +# define _REG_ARG1			"%rdi"
> +# define NATIVE_IDENTITY_32		"mov %edi, %eax"

Yeah, that "identity" looks strange. How about NATIVE_NOOP and
NATIVE_NOOP_32 ?

> +# define NATIVE_USERGS_SYSRET64		"swapgs; sysretq"
> +#else
> +# define _REG_ARG1			"%eax"
> +#endif
> +
> +#define _REG_RET			"%" _ASM_AX
> +
> +#define NATIVE_ZERO			"xor " _REG_ARG1 ", " _REG_ARG1

NATIVE_ZERO_OUT

I guess. NATIVE_ZERO reads like the native representation of 0 :-)

...

-- 
Regards/Gruss,
    Boris.

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