Re: [patch] enabling APIC and NMI watchdog on UP systems

From: Ingo Molnar (mingo@elte.hu)
Date: Fri Sep 29 2000 - 03:00:37 EST


On Fri, 29 Sep 2000, Keith Owens wrote:

> arch/i386/kernel/msr.c has been there since at least 2.4.0-test1. A

there is nothing performance-counter specific about /dev/msr. There is no
highlevel performance-counter logic in the kernel. So if the kernel
decides to use one of them, that should not be more of a problem than some
other user already using the performance counter. You can simply turn
performance counters off via /dev/msr, just like you would clear them
prior use anyway. If there was some existing kernel-based API to give
unpriviledged access to performance counters then i would agree - but
right now it takes extra action by a knowledgable root to use /dev/msr.

> I originally did that but it users have to tweak their boot files
> whenever they install a new kernel. Making it a config option
> propagates the user's requirements from one kernel build to another.

making an extra config option unnecessery litters the kernel with #ifdefs.
Why should it be a config option beyond CONFIG_X86_APIC if our goal is to
run it on as many boxes as possible?

        Ingo

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