Re: Standardizing an MSR or other hypercall to get an RNG seed?

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On 09/19/2014 09:53 AM, Gleb Natapov wrote:
> On Fri, Sep 19, 2014 at 09:40:07AM -0700, H. Peter Anvin wrote:
>> On 09/19/2014 09:37 AM, Gleb Natapov wrote:
>>>
>>> Linux detects what hypervior it runs on very early
>>
>> Not anywhere close to early enough.  We're talking for uses like kASLR.
>>
> Still to early to do:
> 
>    h = cpuid(HYPERVIOR_SIGNATURE)
>    if (h == KVMKVMKVM) {
>       if (cpuid(kvm_features) & kvm_rnd)
>          rdmsr(kvm_rnd)
>    else (h == HyperV) {
>       if (cpuid(hv_features) & hv_rnd)
>         rdmsr(hv_rnd) 
>    else (h == XenXenXen) {
>       if (cpuid(xen_features) & xen_rnd)
>         rdmsr(xen_rnd)
>   }
> 

If we need to do chase loops, especially not so...

	-hpa


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