On 09/19/2014 05:46 PM, H. Peter Anvin wrote: > On 09/19/2014 01:46 PM, Andy Lutomirski wrote: >>> >>> 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. >> > > Yes, the presence of RDRAND implies a cheap and inexhaustible entropy > source.
A guest kernel couldn't make it look like RDRAND is not present to guest userspace? Christopher -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
