Sean Christopherson <sean.j.christopher...@intel.com> writes: > On Mon, Oct 05, 2020 at 05:29:47PM +0200, Vitaly Kuznetsov wrote: >> Tianjia Zhang <tianjia.zh...@linux.alibaba.com> writes: >> >> > Original KVM_SET_CPUID has removed NX on non-NX hosts as it did >> > before. but KVM_SET_CPUID2 does not. The two should be consistent. >> > >> > Signed-off-by: Tianjia Zhang <tianjia.zh...@linux.alibaba.com> >> > --- >> > arch/x86/kvm/cpuid.c | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c >> > index 3fd6eec202d7..3e7ba2b11acb 100644 >> > --- a/arch/x86/kvm/cpuid.c >> > +++ b/arch/x86/kvm/cpuid.c >> > @@ -257,6 +257,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu, >> > goto out; >> > } >> > >> > + cpuid_fix_nx_cap(vcpu); >> > kvm_update_cpuid_runtime(vcpu); >> > kvm_vcpu_after_set_cpuid(vcpu); >> > out: >> >> I stumbled upon this too and came to the conclusion this is >> intentional, e.g. see this: >> >> commit 0771671749b59a507b6da4efb931c44d9691e248 >> Author: Dan Kenigsberg <dan...@qumranet.com> >> Date: Wed Nov 21 17:10:04 2007 +0200 >> >> KVM: Enhance guest cpuid management >> >> ... >> >> [avi: fix original KVM_SET_CPUID not removing nx on non-nx hosts as it >> did >> before] >> >> but this is a very, very old story. > > Doesn't mean it's bogus though :-) _If_ we want to extend this behavior to > KVM_SET_CPUID2, there should be a justified need.
Yes, exactly. I meand to say that founding fathers of KVM left the adjustment for KVM_SET_CPUID exclusively on purpose and not by mistake :-) -- Vitaly
