linux-kernel - Re: [PATCH] x86/cpu/vmware: use the full form of inl in VMWARE

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Message-ID: <MN2PR05MB61419440A3C9FF9CB920BCD5A19B0@MN2PR05MB6141.namprd05.prod.outlook.com>
Date:   Mon, 7 Oct 2019 19:29:25 +0000
From:   Thomas Hellstrom <thellstrom@...are.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>,
        Pv-drivers <Pv-drivers@...are.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
CC:     "hpa@...or.com" <hpa@...or.com>, Kees Cook <keescook@...omium.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] x86/cpu/vmware: use the full form of inl in VMWARE_PORT

On 10/7/19 9:21 PM, Sami Tolvanen wrote:
> LLVM's assembler doesn't accept the short form inl (%%dx) instruction,
> but instead insists on the output register to be explicitly specified:
>
>   <inline asm>:1:7: error: invalid operand for instruction
>           inl (%dx)
>              ^
>   LLVM ERROR: Error parsing inline asm
>
> Use the full form of the instruction to fix the build.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Acked-by: Thomas Hellstrom <thellstrom@...are.com>

> ---
>  arch/x86/kernel/cpu/vmware.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index 9735139cfdf8..46d732696c1c 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -49,7 +49,7 @@
>  #define VMWARE_CMD_VCPU_RESERVED 31
>  
>  #define VMWARE_PORT(cmd, eax, ebx, ecx, edx)				\
> -	__asm__("inl (%%dx)" :						\
> +	__asm__("inl (%%dx), %%eax" :					\
>  		"=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) :		\
>  		"a"(VMWARE_HYPERVISOR_MAGIC),				\
>  		"c"(VMWARE_CMD_##cmd),					\