Re: [Xen-devel] rdmsr general protection error

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

On Tue, May 03, 2016 at 11:01:32PM +0800, Big Strong wrote:
> I want to test if my processor support VMFUNC which is described as:
> >
> >
> > The IA32_VMX_VMFUNC MSR exists only on processors that support the
> > 1-setting of the “activate secondary controls” VM-execution control (only 
> > if*
> > bit 63 of the IA32_VMX_PROCBASED_CTLS MSR is 1*) and the 1-setting of the
> > “enable VM functions” secondary processor-based VM-execution control (only
> > if* bit 45 of the IA32_VMX_PROCBASED_CTLS2 MSR is 1*).
> 
> 
> So in order to do that, I need to use rdmsr as follows:
> 
> //IA32_VMX_PROCBASED_CTLS
> >  __asm__ __volatile__("rdmsr" : "=a" (eax), "=d" (edx) : "c" (0x482));
> 
> //IA32_VMX_PROCBASED_CTLS 2
> 
>  __asm__ __volatile__("rdmsr" : "=a" (eax), "=d" (edx) : "c" (0x48B));
> 
> 
> But both the rdmsr instruction would cause a #GP, even when I run it from
> the native linux as a root user and without xen running.
> 
> So is there a way to use the rdmsr in dom0?

Did you try using the /sysfs MSR entries?

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