Why is PCE not set in CR4?

Bruce M Simpson bms at spc.org
Wed Oct 1 05:41:34 PDT 2003


[crossposting trimmed]

On Wed, Oct 01, 2003 at 12:41:56PM +0100, Bruce M Simpson wrote:
> > I have read the perfmon documentation and source code. For several 
> > reasons, I do not think it is totally adequate in my situation.
> This is an extension to the i386_vm86() syscall which will let you turn
> PCE on and off if you're the superuser.

Now that I think on this a bit more, a sysctl might be a better place to
put this, but it seemed to belong with the i386_vm86() bits, rather than
polluting initcpu.c right away.

Mind you, if you're going to hack perfmon, perhaps putting this in initcpu
isn't such a bad idea after all, with a loader tunable instead. That way
perfmon can pickup on the tunable when attached by nexus during boot.

A few people want to see i386_vm86() die. Its death is inevitable given
x86-64 and the other new platforms. So perhaps the other way is better.

In any event, I reconsider my decision to commit the code, and simply
offer it as an example of one way to do things, not necessarily the
right way.

BMS


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