On Wed, Sep 14, 2016 at 3:03 PM, Kyle Huey <m...@kylehuey.com> wrote: > On Wed, Sep 14, 2016 at 2:35 PM, Dave Hansen > <dave.han...@linux.intel.com> wrote: >> On 09/14/2016 02:01 PM, Kyle Huey wrote:
>> Is any of this useful to optimize away at compile-time? We have config >> options for when we're running as a guest, and this seems like a feature >> that isn't available when running on bare metal. > > On the contrary, this is only available when we're on bare metal. > Neither Xen nor KVM virtualize CPUID faulting (although KVM correctly > suppresses MSR_PLATFORM_INFO's report of support for it). KVM could easily support this. If rr starts using it, I think KVM *should* add support, possibly even for older CPUs that don't support the feature in hardware. It's too bad that x86 doesn't give us the instruction bytes on a fault. Otherwise we could lazily switch this feature. --Andy
