KVM: x86: Make math work for other scales

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The math in kvm_get_time_scale relies on the fact that
NSEC_PER_SEC < 2^32.  To use the same function to compute
arbitrary time scales, we must extend the first reduction
step to shrink the base rate to a 32-bit value, and
possibly reduce the scaled rate into a 32-bit as well.

Note we must take care to avoid an arithmetic overflow
when scaling up the tps32 value (this could not happen
with the fixed scaled value of NSEC_PER_SEC, but can
happen with scaled rates above 2^31.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

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Zachary Amsden 2010-09-18 14:38:13 -10:00 • committed by Avi Kivity

parent 624d84cfe6

commit 5f4e3f8827

1 changed files with 18 additions and 12 deletions

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arch/x86/kvm/x86.c

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