linux-kernel - Re: [PATCH v5 05/12] x86/mm: add INVLPGB support code

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Message-ID: <44837964d67d6f35a20139fbe310f621141a0404.camel@surriel.com>
Date: Fri, 17 Jan 2025 09:20:13 -0500
From: Rik van Riel <riel@...riel.com>
To: kernel test robot <lkp@...el.com>
Cc: llvm <llvm@...ts.linux.dev>, x86 <x86@...nel.org>, Borislav Petkov
	 <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, Peter Zijlstra
	 <peterz@...radead.org>, kernel-team <kernel-team@...a.com>, 
 "linux-kernel@...r.kernel.org"
	 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 05/12] x86/mm: add INVLPGB support code

On Fri, 2025-01-17 at 11:37 +0800, kernel test robot wrote:
> 
> compiler: clang version 19.1.3
> (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b25
> 4b6afab99)
> reproduce (this is a W=1 build):
> (https://download.01.org/0day-ci/archive/20250117/202501171121.nQcwVI
> 41-lkp@...el.com/reproduce)
> 

> > > arch/x86/include/asm/invlpgb.h:26:49: error: invalid input size
> > > for constraint 'a'
>       26 |         asm volatile(".byte 0x0f, 0x01, 0xfe" : : "a"
> (rax), "c" (ecx), "d" (edx));
>          |                                                        ^
> 

What do I do about this?

It didn't used to complain when we had a named
assembler operator there:

    asm volatile("invlpgb" : : "a" (rax), "c" (ecx), "d" (edx));

However, now that we're using .byte for compatibility
with older binutils, things break with newer llvm?

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