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RE: [Xen-devel] [PATCH] Fix build failure in 32 environment

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Fix build failure in 32 environment
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Mon, 14 Dec 2009 08:52:50 -0800 (PST)
Cc: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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> > If I remember correctly, rdtscp is a valid instruction
> > in 32-bit mode so why are you disabling support for
> > 32-bit Xen?
> > 
> > Personally, I don't care if 32-bit Xen is supported,
> > but either we need to say it is supported or it is
> > not supported, not have new features randomly choose
> > to support it or not, especially features that have
> > impact on userland applications.
> It can be supported for existign features but not all new ones. We can
> perhaps retire it all together after 4.0.

IMHO, this is not a new feature, this is an ABI incompatibility
issue. If rdtscp is a valid 32-bit instruction, IMHO it
should either work on both 32-bit Xen and 64-bit Xen or

Was this patch a quick hack to allow the code to compile
for 32-bit Xen or was it a reasoned decision to disallow
support on 32-bit Xen?

(And, in any case, if rdtscp is a "new feature", why was
the patch accepted post-freeze, especially when there
is still lively debate going on? ;-)

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