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Subject: Re: [tip:x86/urgent] x86-64, build: Always pass in -mno-sse
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Wed, 04 Dec 2013 07:31:28 -0800
To: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        tglx@linutronix.de, hpa@linux.intel.com, kevin.b.smith@intel.com,
        hjl.tools@gmail.com
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I can regenerate the patch if you want.

Ingo Molnar <mingo@kernel.org> wrote:
>
>* tip-bot for H. Peter Anvin <tipbot@zytor.com> wrote:
>
>> Commit-ID:  5551a34e5aeab868f8d37f70d8754868921b4ee5
>> Gitweb:    
>http://git.kernel.org/tip/5551a34e5aeab868f8d37f70d8754868921b4ee5
>> Author:     H. Peter Anvin <hpa@linux.intel.com>
>> AuthorDate: Wed, 20 Nov 2013 13:31:49 -0800
>> Committer:  H. Peter Anvin <hpa@linux.intel.com>
>> CommitDate: Tue, 3 Dec 2013 17:40:22 -0800
>> 
>> x86-64, build: Always pass in -mno-sse
>> 
>> Always pass in the -mno-sse argument, regardless if
>> -preferred-stack-boundary is supported.  We never want to generate
>SSE
>> instructions in the kernel unless we *really* know what we're doing.
>> 
>> According to H. J. Lu, any version of gcc new enough that we support
>> it at all should handle the -mno-sse option, so just add it
>> unconditionally.
>> 
>> Reported-by: Kevin B. Smith <kevin.b.smith@intel.com>
>> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
>> Cc: H. J. Lu <hjl.tools@gmail.com>
>> Link:
>http://lkml.kernel.org/n/tip-j21wzqv790q834n7yc6g80j1@git.kernel.org
>> Cc: <stable@vger.kernel.org> # build fix only
>> ---
>>  arch/x86/Makefile | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>> index 41250fb..eda00f9 100644
>> --- a/arch/x86/Makefile
>> +++ b/arch/x86/Makefile
>> @@ -31,6 +31,9 @@ ifeq ($(CONFIG_X86_32),y)
>>  
>>          KBUILD_CFLAGS += -msoft-float -mregparm=3
>-freg-struct-return
>>  
>> +        # Don't autogenerate SSE instructions
>> +	KBUILD_CFLAGS += -mno-sse
>> +
>>          # Never want PIC in a 32-bit kernel, prevent breakage with
>GCC built
>>          # with nonstandard options
>>          KBUILD_CFLAGS += -fno-pic
>> @@ -57,8 +60,11 @@ else
>>          KBUILD_AFLAGS += -m64
>>          KBUILD_CFLAGS += -m64
>>  
>> +        # Don't autogenerate SSE instructions
>> +	KBUILD_CFLAGS += -mno-sse
>> +
>>  	# Use -mpreferred-stack-boundary=3 if supported.
>> -	KBUILD_CFLAGS += $(call cc-option,-mno-sse
>-mpreferred-stack-boundary=3)
>> +	KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=3)
>>  
>>          # FIXME - should be integrated in Makefile.cpu
>(Makefile_32.cpu)
>>          cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)
>
>Just a detail I noticed: in kbuild we intentionally use 8 spaces for 
>tabs in Makefiles and only use tabs for commands where tabs are 
>required.
>
>The above code introduces tabs in the middle of 8-space sequences. It 
>works but is inconsistent.
>
>Thanks,
>
>	Ingo

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.