On 07/03/2018 15:56, Radim Krčmář wrote: > The MSR_F10H_DECFG default is questionable -- MSR_F10H_DECFG is an > architectural MSR, so we'd be changing the guest under the sight of > existing userspaces. > A potential security risk if they migrate the guest to a CPU that > doesn't serialize LFENCE. ARCH_CAPABILITIES are at least hidden by a > new CPUID bit. Good point. Perhaps we should add a KVM-specific CPUID bit for serializing LFENCE. > The feature MSR defaults are going to be a mess anyway: we have > MSR_IA32_UCODE_REV that is tightly coupled with CPUID. Not a good > candidate for passing by default and currently also has a default value. Yeah, ucode revision is out of question. Paolo
