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Date: Wed, 17 Jun 2009 10:06:44 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Huang Ying <ying.huang@intel.com>,
       Herbert Xu <herbert@gondor.apana.org.au>,
       Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
       linux-crypto@vger.kernel.org
Subject: Re: [RFC 6/7] x86: Move kernel_fpu_using to asm/i387.h
References: <1244704236.5320.129.camel@yhuang-dev.sh.intel.com> <20090617164622.GB25357@elte.hu>
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Ingo Molnar wrote:
>>  
>> +static inline int kernel_fpu_using(void)
>> +{
>> +	if (in_interrupt() && !(read_cr0() & X86_CR0_TS))
>> +		return 1;
>> +	return 0;
>> +}
>> +
> 
> Looks sane to me. Herbert, do you ack it?
> 

Although I have to say, the structure of:

if (boolean test)
	return 1;
return 0;

... truly was hit with the ugly stick.  It really should be:

static inline bool kernel_fpu_using(void)
{
	return in_interrupt() && !(read_cr0() && C86_CR0_TS);
}

Huang: if I recall correctly, these functions were originally designed
to deal with the fact that VIA processors generate spurious #TS faults
due to broken design of the Padlock instructions.  The AES and PCLMUL
instructions actually use SSE registers and so will require different
structure.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.