On 30/11/18 21:41, Eric Northup wrote: > On Mon, Nov 5, 2018 at 10:01 PM Liu Jingqi <jingqi.liu@xxxxxxxxx> wrote: >> >> Direct stores instructions MOVDIRI and MOVDIR64B will be available in >> Tremont and other future x86 processors, >> and need to be exposed to guest VM. > > It seems like KVM's emulator should be able to complete these > instructions to emulated MMIO before exposing CPUID to guests in any > default or supported configurations. > > It'll be much simpler for usermode to implement that property if the > KVM-reported supported CPUID table doesn't get updated before the KVM > emulator does. We already do not support emulation for many CPUID bits we expose (AVX and AVX512 above all), so that's not a huge problem. I suppose these instructions are unlikely to be used on MMIO areas such as legacy VGA VRAM. Paolo
