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SubjectRe: [miniPATCH] about cr4 : SysRq Show Reg
On Thu, 15 Jul 1999, Masahiro Adegawa wrote:

> we get cr4 when `SysRq: Show Regs'.
> But I do not know the best effective judging conditions of CR4.

You should probably use a bit mask. It seems X86_FEATURE_VME is best for
Intel CPUs as all Intels that have CR4 implement this feature while there
exist Intel CPUs that do have CR4 but do not support X86_FEATURE_PSE. But
I am not sure about other vendors.

To be on the safe side I would test features that have their respective
CR4 bits and assume it's present whenever any of them is set. AFAIK, the
appropriate mask is: (X86_FEATURE_VME | X86_FEATURE_DE | X86_FEATURE_PSE |
X86_FEATURE_TSC | X86_FEATURE_PAE | X86_FEATURE_MCE | X86_FEATURE_PGE |
X86_FEATURE_FXSR | X86_FEATURE_25).

X86_FEATURE_25 will probably called X86_FEATURE_XMM one day.

--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +


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