From: "H. Peter Anvin" <hpa@transmeta.com>
To: Quim K Holland <qkholland@my-deja.com>
Cc: dledford@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org
Subject: Re: cpu_has_fxsr or cpu_has_xmm?
Date: Fri, 23 Feb 2001 13:44:14 -0800 [thread overview]
Message-ID: <3A96D9AE.C320EC1@transmeta.com> (raw)
In-Reply-To: <200102232051.MAA18803@mail17.bigmailbox.com>
Quim K Holland wrote:
>
> 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?
>
No, because the CPU *may* overwrite it when you do an FXSAVE.
-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
next prev parent reply other threads:[~2001-02-23 21:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-23 20:51 cpu_has_fxsr or cpu_has_xmm? Quim K Holland
2001-02-23 21:44 ` H. Peter Anvin [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-02-23 5:38 Quim K Holland
2001-02-23 6:11 ` H. Peter Anvin
2001-02-23 11:23 ` Doug Ledford
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