Re: [GIT PULL] x86 fixes for 2.6.30-rc8

From: H. Peter Anvin
Date: Sat May 30 2009 - 15:25:00 EST

Michael S. Zick wrote:
> On Sat May 30 2009, Pavel Machek wrote:
>> Hi!
>>> --- a/Documentation/kernel-parameters.txt
>>> +++ b/Documentation/kernel-parameters.txt
>>> @@ -1535,6 +1535,10 @@ and is between 256 and 4096 characters. It is defined in the file
>>> register save and restore. The kernel will only save
>>> legacy floating-point registers on task switch.
>>> + noxsave [BUGS=X86] Disables x86 extended register state save
>>> + and restore using xsave. The kernel will fallback to
>>> + enabling legacy floating-point and sse state.
>>> +
>> Does that mean apps using sse8 will see their registers corrupted if
>> this option is used? Or are new registers sets always added in a way
>> that kernel has to enable them first?

New register sets always require enabling.

> Has this change been tested on the processors that have independent ftp&sse
> units, without the shared registers? Such as the VIA C7-M?

x87 and SSE are always separate. Whether or not register sets are
separate is an architectural issue, and isn't subject to variation
across CPUs.


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

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