[Xen-ia64-devel][PATCH] Emulate PAL_HALT_LIGHT

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Alex,
This patch intends to use do_block to emulate Guest PAL_HALT_LIGHT,
whenever there is an interrupt for this vcpu, this vcpu is woken up.

Signed-off-by: Anthony Xu <anthony.xu@xxxxxxxxx>


And, I noticed domU use do_yield to emulate Guest PAL_HALT_LIGHT,
There is no correctness issue, but may impact performance when HT is enabled.
If there are a domU vcpu and idle vcpu running on one LP, 
Then Guest PAL_HALT_LIGHT will become a tight loop,that means this LP
will not yield resource to the other LP on the same core even when there is
no task running on this LP. This will impact the whole system performance 
dramatically. VTI-domain had suffered this penalty due to the similar reason.

I propose to use do_block to emulate Guest PAL_HALT_LIGHT.

Thanks,
Anthony

Attachment: emulate_PAL_HALT_LIGHT.patch
Description: emulate_PAL_HALT_LIGHT.patch

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