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[Xen-devel] Re: [Qemu-devel] [PATCH 1/2] xenner: add event channel imple

To: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Qemu-devel] [PATCH 1/2] xenner: add event channel implementation.
From: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Date: Tue, 26 Aug 2008 15:13:40 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, qemu-devel@xxxxxxxxxx
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Ian Jackson wrote:
> Gerd Hoffmann writes ("[Qemu-devel] [PATCH 1/2] xenner: add event channel 
> implementation."):
>> The patch also adds a XenEvtOps struct with function pointers for the
>> xc_evtchn_* family, which is used to switch between libxenctrl and the
>> qemu implementation at runtime.  By default libxenctrl is used.
> I don't understand why it's necessary to switch between these two
> modes at runtime.  That adds a lot of extra boilerplate and
> indirection code and probably has some tiny performance effect too.
> Why not make it a compile-time option ?

IMHO compile time options are a usability nightmare in most cases.

Note that in another mail you've asked for a command line switch for
qemu to enable xen emulation mode even when running on xen.  That
wouldn't work any more if we would make this a compile time option.  You
would have to go and rebuild qemu first.

Also distrubutions would have to ship two binaries instead of one.  And
there are already way to much different qemu binaries today.  I want to
get that number down, not up.


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