Date: Fri, 23 Feb 2001 12:51:05 -0800
Message-Id: <200102232051.MAA18803@mail17.bigmailbox.com>
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From: "Quim K Holland" <qkholland@my-deja.com>
To: dledford@redhat.com
Cc: hpa@zytor.com, linux-kernel@vger.kernel.org
Subject: Re: cpu_has_fxsr or cpu_has_xmm?
Sender: linux-kernel-owner@vger.kernel.org

>>>>> "DL" == Doug Ledford <dledford@redhat.com> writes:
>> > --- linux.vanilla/arch/i386/kernel/i387.c       Thu Feb 22 09:05:35 2001
>> > +++ linux.ac/arch/i386/kernel/i387.c    Sun Feb  4 10:58:36 2001
>> > @@ -179,7 +179,7 @@
>> >
>> >  unsigned short get_fpu_mxcsr( struct task_struct *tsk )
>> >  {
>> > -       if ( cpu_has_fxsr ) {
>> > +       if ( cpu_has_xmm ) {
>> >                 return tsk->thread.i387.fxsave.mxcsr;
>> >         } else {
>> >                 return 0x1f80;
>> >

DL> As to the correctness, the mxcsr register really only exists
DL> if you have xmm, so the xmm is the correct test. However,...

DL> ...  User space programmers should be checking for xmm
DL> capability themselves before ever paying attention to mxcsr
DL> anyway, so it's not an end of the world error.

If that is the case, wouldn't it be simpler to always return
tsk->thread.i387.fxsave.mxcsr from this function, and initialize
that field to 0x1f80 (whatever that magic number means) when
the structure is built?


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