[Xen-devel] [PATCH] Move ACPI timer to HV

["Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>]

Keir,

The patch moves ACPI timer to HV, which is the last platform timer in
Qemu.

We found Vista polls ACPI timer very frequently (about 15 times
averagely) when handling timer (RTC @ 64HZ) interrupt routine. Though
the exact reason is known, it should be related to system time
adjustment. When it's in Qemu, the overhead is big. After moving,
Vista's idle overhead decreases dramatically from ~10% to 0.9%. 

Another benefit is that Vista can only pass Performance rating with this
patch. The root cause is that ACPI timer in Qemu isn't synchronous with
other platform timer in HV, which results in Vista complains "can't
measure TSC frequency".

This patch changes vpit.h to vpt.h, for it not only has pit structure in
it, but other platform timer's structure. Another change is moving ACPI
timer and related address from acpi.h to ioreq.h, which can be shared by
HV and ACPI firmware. What do you think of it?

Signed-off-by: Xiaowei Yang <xiaowei.yang@xxxxxxxxx>

Thanks, 
Xiaowei

Attachment: pmt.patch
Description: pmt.patch

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