On 10/11/2017 07:07, Wanpeng Li wrote: >>> You should also add a cpuid flag in kvm part. >> It is better without that. The flag has no dependency on KVM (kernel >> hypervisor) code. > Do you mean -cpu host, +xxxx，I think it will result in "warning: host > doesn't support requested feature: CPUID.40000001H:eax.XXXXXX" There are some exceptions where QEMU overrides the values of KVM_GET_SUPPORTED_CPUID. I think it is better to add the flag to KVM *and* to QEMU's override in kvm_arch_get_supported_cpuid (target/i386/kvm.c). Paolo
