> -----Original Message----- > From: Andy Lutomirski [mailto:luto@xxxxxxxxxxxxxx] > Sent: Thursday, September 18, 2014 8:38 AM > To: H. Peter Anvin > Cc: KY Srinivasan; Linux Virtualization; kvm list; Gleb Natapov; Paolo Bonzini; > Theodore Ts'o > Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed? > > On Thu, Sep 18, 2014 at 7:43 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > > On 09/18/2014 07:40 AM, KY Srinivasan wrote: > >>> > >>> The main questions are what MSR index to use and how to detect the > >>> presence of the MSR. I've played with two approaches: > >>> > >>> 1. Use CPUID to detect the presence of this feature. This is very > >>> easy for KVM to implement by using a KVM-specific CPUID feature. > >>> The problem is that this will necessarily be KVM-specific, as the > >>> guest must first probe for KVM and then probe for the KVM feature. > >>> I doubt that Hyper-V, for example, wants to claim to be KVM. If we > >>> could standardize a non- hypervisor-specific CPUID feature, then this > problem would go away. > >> > >> We would prefer a CPUID feature bit to detect this feature. > >> > > > > I guess if we're introducing the concept of pan-OS MSRs we could also > > have pan-OS CPUID. The real issue is to get a single non-conflicting > > standard. > > Agreed. > > KVM currently puts 0 in 0x40000000.EAX, meaning that a feature bit in > Microsoft's leaf 0x40000003 would probably not work well for KVM. I don't > expect that Microsoft wants to start claiming to be KVM for the purpose of > using a KVM-style feature bit, so, if we went the CPUID route, we would > probably need something new. > > --Andy I am copying other Hyper-V engineers to this discussion. Regards, K. Y > > > > > -hpa > > > > > > > > -- > Andy Lutomirski > AMA Capital Management, LLC ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
