Re: [Xen-devel] cpuinfo flags change under 3.2-testing?

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

We're just better at hiding CPU features which are unusable by the dom0
guest now. For example, since it is a 32-bit kernel, we hide the long-mode
feature from it, and related features. We also used to advertise
machine-check support, for example, but don't expose the usual hardware
interface to it to dom0.

 -- Keir

On 13/9/08 06:21, "Carl Jones" <carl.jones@xxxxxxxxx> wrote:

> Hi,
> 
> I'm building Xen on a 64bit machine, then using the xen.gz from that
> on a 32bit host (so that it can boot 64bit guests). This works fine.
> However I note that after booting xen.gz from 3.2-testing
> /proc/cpuinfo has different flags. 3.2.1 is the same. I have not yet
> tried 3.3.x.
> 
> 3.2.0 results in:
> flags             : fpu de tsc msr pae mce cx8 apic sep mtrr mca cmov
> pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
> lm constant_tsc pni monitor ds_cpl vmx tm2 cx16 xtpr lahf_lm
> 
> 3.2-testing (currently 3.2.2-rc5-pre):
> flags             : fpu de tsc msr pae cx8 apic sep mtrr cmov pat
> clflush acpi mmx fxsr sse sse2 ss ht nx constant_tsc pni
> 
> To build I'm grabbing the source from xen.org then simply doing a
> 'make' from xen/.
> 
> Build machine is a Dual Opteron, running CentOS 5.x x86_64. Machine
> that I'm booting it on is Dual Xeon Woodcrest, running CentOS 5.x i386
> with a 2.6.18.8 32bit dom0 kernel pulled from xen.org.
> 
> # xm info | grep cap
> hw_caps                :
> bfebfbff:20100800:00000000:00000140:0004e33d:00000000:00000001
> xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
> 
> # uname -m
> i686
> 
> # uname -a
> Linux host194 2.6.18.8-xen0 #1 Sat Sep 13 00:22:21 UTC 2008 i686 i686
> i386 GNU/Linux
> 
> Is this a bug or is there perhaps some build option I should be using?
> 
> Regards,
> Carl
> 
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