On 07/16/2014 09:21 AM, Gleb Natapov wrote: > On Wed, Jul 16, 2014 at 09:13:23AM -0700, H. Peter Anvin wrote: >> On 07/16/2014 09:08 AM, Paolo Bonzini wrote: >>> Il 16/07/2014 18:03, H. Peter Anvin ha scritto: >>>> 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." >>> >>> But those will set the CPUID bit. There is currently no way for KVM >>> guests to know if a CPUID bit is real or emulated. >>> >> >> OK, so there wasn't any protocol implemented in the end. I sit corrected. >> > That protocol that was implemented is between qemu and kvm, not kvm and a guest. > Either which way, the notion was to have a PV CPUID bit like the proposed kvm_get_rng_seed bit, but to have it exercised by executing RDRAND. The biggest reason to *not* do this would be that with an MSR it is not available to guest user space, which may be better under the circumstances. -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
