On 25.11.2008, at 12:48, Andi Kleen wrote:
Why does hpet need to be slow? Can't you just 1:1 pass through one of
the hpet timers if you only have a limited amount of vms?
HPET is not a truly virtualizable device, it's all the counters
in one block that cannot be really mapped to different people.
Right, you'd have to remap stuff on non-page boundaries which is
probably pretty hard to do. Otherwise you wouldn't gain anything,
since you'd still have exits to reprogram the hpet.
Also most systems have very little counters and Linux typically
needs two
at least (system timer and /dev/hpet)
Well, IIRC 3 is a pretty normal amount and blocking /dev/hpet if the
hpet is in use shouldn't be a problem.
But yeah - the remapping of HPET timers to virtual HPET timers sounds
pretty tough. I wonder if one could overcome that with a little
hardware support though ...
Alex
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