RE: [PATCH] softtsc (was RE: Guest TSC and Xen (Intel and AMD feedback please))

["Dan Magenheimer" <dan.magenheimer@oracle.com>]

> Yes, I will take it, but have the following comments.
>  2. Your change in common/keyhandler.c breaks ia64. :-)

Oops! ;-)  What's the best way to handle this?  It would
be unfortunate to lose valuable debug data just because its
arch-dependent but I don't see any other arch-dependent code
in keyhandler.c and I'll bet you don't want to start adding
ifdef's nor introduce arch/xxx/keyhandler.c just for this.

>  1. Why do you define new boolean 'constant_tsc'? Can you just use
> test_bit(X86_FEATURE_CONSTANT_TSC)?
>  3. Your change to arch/x86/time.c looks unnecessary.

I was thinking that the tests for these features should probably
be abstracted (e.g. static inline in a header file or a
global function), but wasn't sure about the best way to deal
with the datatypes (e.g. struct cpuinfo_x86) so defaulted to
global variables.

Both globals are simply for debug output in keyhandler.c
so depending on the answer to (2) above, those patch-parts
could just go away.

>  4. Should you catch SVM's RDTSCP vmexit as well as RDTSC?

I thought I remembered seeing code that reported/lied to guests
that the rdtscp feature was not present?

Thanks,
Dan