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Re: [Xen-devel] Re: APIC rework

To: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] Re: APIC rework
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 17 Nov 2009 13:05:06 +0000
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Han, Weidong" <weidong.han@xxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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Thread-topic: [Xen-devel] Re: APIC rework
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On 17/11/2009 12:46, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> wrote:

>> If Xen can set the interrupt triggering by itself, why would it ever
>> need dom0 to do it?  Couldn't it just preconfigure all the pins, and
>> then wait for dom0 to provide/request the pirq<->evtchn mapping?
> After reviewing the logic, I think we can use DOMID_SELF to identify new dom0.
> In linux-2.6.18 dom0, only qemu uses this hypercall for device assginment, so
> map->domid shouldn't be dom0.  If old dom0/qemu with this hypercall, keeps the
> logic unchanged, and only change the logic for new dom0 when call into it.
> Attached the patch.

Don't like it (subtle semantic difference based on domid field is very odd
and could bite us later), and actually now I look closer I don't like the
original patch much either, if only because it does clearly change the
interface for MAP_PIRQ_TYPE_GSI by adding trigger/polarity flags (and not
documented or exported properly in the physdev.h header file).

I need to take a step back and work out what in fact you're trying to
achieve. I'm going to revert the original patch from xen-unstable. If such
an interface extension is really required, I think at least the new
interface should be a new subtype of MAP_PIRQ_TYPE_xxx, properly described
in the header file. But like I say, I don't know what the patch is even
really trying to do or overcome.

 -- Keir

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