Messages in this thread | | | Subject | Re: [PATCH 02/15] KVM: x86: Emulate RDPID only if RDTSCP is supported | From | Paolo Bonzini <> | Date | Wed, 5 May 2021 10:01:54 +0200 |
| |
On 05/05/21 05:51, Reiji Watanabe wrote: >> --- a/arch/x86/kvm/cpuid.c >> +++ b/arch/x86/kvm/cpuid.c >> @@ -637,7 +637,8 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func) >> case 7: >> entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; >> entry->eax = 0; >> - entry->ecx = F(RDPID); >> + if (kvm_cpu_cap_has(X86_FEATURE_RDTSCP)) >> + entry->ecx = F(RDPID); >> ++array->nent; >> default: >> break; > I'm wondering if entry->ecx should be set to F(RDPID) here > even if the CPU supports RDPID natively. > (i.e. kvm_cpu_cap_has(X86_FEATURE_RDPID) is true) > > The document "Documentation/virt/kvm/api.rst" says: > --- > 4.88 KVM_GET_EMULATED_CPUID > --------------------------- > <...> > Userspace can use the information returned by this ioctl to query > which features are emulated by kvm instead of being present natively. > ---
Setting it always is consistent with the treatment of MOVBE above. Either way is okay but it should be done for both bits.
Paolo
| |