On 07/16/2014 07:07 AM, Andy Lutomirski wrote: > > This patch has nothing whatsoever to do with how much I trust the CPU > vs the hypervisor. It's for the enormous installed base of machines > without RDRAND. > > hpa suggested emulating RDRAND awhile ago, but I think that'll > unusably slow -- the kernel uses RDRAND in various places where it's > expected to be fast, and not using it at all will be preferable to > causing a VM exit for every few bytes. I've been careful to only use > this in the guest in places where a few hundred to a few thousand > cycles per 64 bits of RNG seed is acceptable. > I suggested emulating RDRAND *but not set the CPUID bit*. We already developed a protocol in KVM/Qemu to enumerate emulated features (created for MOVBE as I recall), specifically to service the semantic "feature X will work but will be substantially slower than normal." -hpa -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
