Re: [Xen-devel] Different CPU flags between Dom0 and DomU?

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Mar 04, 2013 at 02:09:06PM +0900, Choonho Son wrote:
> Hi all,
> 
> I have a machine with Intel Xeon E5-2630. Intel E5-series supports
> AVX(Advanced Vector eXtension). And Xen Hypervisor 4.1 also supports
> AVX feature.

Lets CC the Intel folks since these two git commits point to them:

commit 25050f53be29518a3c9bdd0628333cd3121d2750
Author: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
Date:   Tue Dec 6 11:27:18 2011 +0000

    X86: expose Intel new features to pv/hvm
    
    Intel recently release some new features, including
    FMA/AVX2/BMI1/BMI2/LZCNT/MOVBE.
    Refer to http://software.intel.com/file/36945
    This patch expose these new features to pv and hvm.
    
    Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
    Committed-by: Keir Fraser <keir@xxxxxxx>

commit 500161db50e3430026b5374462c1bdac00257abe
Author: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
Date:   Thu Dec 1 12:21:24 2011 +0100

    X86: expose Intel new features to dom0
    
    This patch expose Intel new features to dom0, including
    FMA/AVX2/BMI1/BMI2/LZCNT/MOVBE.
    
    Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
    Committed-by: Jan Beulich <jbeulich@xxxxxxxx>


> 
> /proc/cpuinfo shows the supported features:
> 
> - Bare-metal Linux (/proc/cpuinfo)
> flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca
> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall
> nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good
> xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl
> vmx smx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 x2apic popcnt
> aes xsave avx lahf_lm ida arat xsaveopt pln pts dts tpr_shadow vnmi
> flexpriority ept vpid
> 
> - Dom0 (/proc/cpuinfo)
> flags           : fpu de tsc msr pae mce cx8 apic sep mca cmov pat
> clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc
> rep_good nopl nonstop_tsc eagerfpu pni pclmulqdq monitor est ssse3
> cx16 sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx
> hypervisor lahf_lm ida arat xsaveopt pln pts dtherm
> 
> - DomU (/proc/cpuinfo)
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp lm
> constant_tsc pni ssse3 cx16 sse4_1 sse4_2 popcnt lahf_lm
> 
> 
> [Questions]
> 
> 1) Why CPU flags are different among bare-metal, dom0, and domU?
> 2) How can I use avx in DomU?
> 3) How CPU flags are delivered from Dom0(or Hypervisor) to DomU?
> 
> [reference]
> http://blog.xen.org/index.php/2011/03/25/xen-4-1-releases/
> 
> Thanks,
> 
> Choonho Son
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

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