Il 19/09/2014 22:46, Andy Lutomirski ha scritto: >> > >> > However, it sounds to me that at least for KVM, it is very easy just to >> > emulate the RDRAND instruction. The hypervisor would report to the guest >> > that RDRAND is supported in CPUID and the emulate the instruction when >> > guest executes it. KVM already traps guest #UD (which would occur if >> > RDRAND executed while it is not supported) - so this scheme wouldn’t >> > introduce additional overhead over RDMSR. > Because then guest user code will think that rdrand is there and will > try to use it, resulting in abysmal performance.
KVM could expose a CPUID leaf that says "RDRAND is not there, but if you execute it the hypervisor will try to do something slow but sane". Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
