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

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Fix build failure in 32 environment
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 14 Dec 2009 17:45:43 +0000
Cc: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 14/12/2009 16:52, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> 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
> neither.

It only needs to work if we advertise RDTSCP in CPUID. Which we don't for
32-bit hosts. There's really nothing wrong with the patch that I can see.
I'd rather have the CPUID frobbing in xc_cpuid_x86.c, but it's a minor
concern. 

 -- Keir



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