On Thu, Sep 18, 2014 at 10:20 AM, KY Srinivasan <kys@xxxxxxxxxxxxx> wrote: > > >> -----Original Message----- >> From: Paolo Bonzini [mailto:paolo.bonzini@xxxxxxxxx] On Behalf Of Paolo >> Bonzini >> Sent: Thursday, September 18, 2014 10:18 AM >> To: Nakajima, Jun; KY Srinivasan >> Cc: Mathew John; Theodore Ts'o; John Starks; kvm list; Gleb Natapov; Niels >> Ferguson; Andy Lutomirski; David Hepkin; H. Peter Anvin; Jake Oshins; Linux >> Virtualization >> Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed? >> >> Il 18/09/2014 19:13, Nakajima, Jun ha scritto: >> > In terms of the address for the MSR, I suggest that you choose one >> > from the range between 40000000H - 400000FFH. The SDM (35.1 >> > ARCHITECTURAL MSRS) says "All existing and future processors will not >> > implement any features using any MSR in this range." Hyper-V already >> > defines many synthetic MSRs in this range, and I think it would be >> > reasonable for you to pick one for this to avoid a conflict? >> >> KVM is not using any MSR in that range. >> >> However, I think it would be better to have the MSR (and perhaps CPUID) >> outside the hypervisor-reserved ranges, so that it becomes architecturally >> defined. In some sense it is similar to the HYPERVISOR CPUID feature. > > Yes, given that we want this to be hypervisor agnostic. > Actually, that MSR address range has been reserved for that purpose, along with: - CPUID.EAX=1 -> ECX bit 31 (always returns 0 on bare metal) - CPUID.EAX=4000_00xxH leaves (i.e. HYPERVISOR CPUID) -- Jun Intel Open Source Technology Center _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
