RE: [Xen-devel] [PATCH 1/3] PAD helper for native and paravirtplatform

From: Liu, Jinsong
Date: Sun Mar 25 2012 - 22:51:29 EST

Konrad Rzeszutek Wilk wrote:
> On Fri, Feb 17, 2012 at 08:56:43AM +0000, Liu, Jinsong wrote:
>>> From f66a2df1392bbe69426387657a220177be50d58a Mon Sep 17 00:00:00
>>> 2001
>> From: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
>> Date: Fri, 10 Feb 2012 20:32:50 +0800
>> Subject: [PATCH 1/3] PAD helper for native and paravirt platform
>> This patch is PAD (Processor Aggregator Device) helper.
>> It provides a native interface for natvie platform, and a template
>> for paravirt platform, so that os can implicitly hook to proper ops
>> accordingly. The paravirt template will further redirect to Xen pv
>> ops in later patch for Xen core parking.
> Liu,
> With this patch: " xen/enlighten: Expose MWAIT and MWAIT_LEAF if
> hypervisor OKs it." which is now in 3.4-rc0:
> (;a=blobdiff;f=arch/x86/xen/enlighten.c;h=b132ade26f778f2cfec7c2d5c7b6db48afe424d5;hp=4172af8ceeb363d06912af15bf89e8508752b794;hb=d4c6fa73fe984e504d52f3d6bba291fd76fe49f7;hpb=aab008db8063364dc3c8ccf4981c21124866b395)
> it means that now that the drivers/acpi/acpi_pad.c can run
> as is under Xen (as the MWAIT_LEAF is exposed) What is the impact
> of that? Is the monitor call causing a trap to the hypervisor which
> will ignore the call? Or will it have some more worrysome
> consequences?

IMO this patch doesn't affect acpi_pad logic (both native and xen acpi_pad).
For native acpi_pad, it need mwait to enter deep Cx (but irrelative to this patch);
For xen acpi_pad, it doesn't depend on whether hypervisor expose mwait or not. It simply parse 'pur' obj and then hypercall to hypervisor to do rest core_parking things (BTW, hypervisor core parking patches have checkin in as c/s 25095/25096).

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