Re: [PATCH] KVM: X86: Call kvm_x86_ops.cpuid_update() after CPUIDs fully updated

[Xiaoyao Li]

On 5/28/2020 11:22 PM, Paolo Bonzini wrote:
> On 28/05/20 17:19, Xiaoyao Li wrote:
> > kvm_x86_ops.cpuid_update() is used to update vmx/svm settings based on
> > updated CPUID settings. So it's supposed to be called after CPUIDs are
> > fully updated, not in the middle stage.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
>
> Are you seeing anything bad happening from this?

Not yet.

IMO changing the order is more reasonable and less confusing.

> Paolo
>
> > ---
> >   arch/x86/kvm/cpuid.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index cd708b0b460a..753739bc1bf0 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -208,8 +208,11 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
> >   	vcpu->arch.cpuid_nent = cpuid->nent;
> >   	cpuid_fix_nx_cap(vcpu);
> >   	kvm_apic_set_version(vcpu);
> > -	kvm_x86_ops.cpuid_update(vcpu);
> >   	r = kvm_update_cpuid(vcpu);
> > +	if (r)
> > +		goto out;
> > +
> > +	kvm_x86_ops.cpuid_update(vcpu);
> >   
> >   out:
> >   	vfree(cpuid_entries);
> > @@ -231,8 +234,11 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
> >   		goto out;
> >   	vcpu->arch.cpuid_nent = cpuid->nent;
> >   	kvm_apic_set_version(vcpu);
> > -	kvm_x86_ops.cpuid_update(vcpu);
> >   	r = kvm_update_cpuid(vcpu);
> > +	if (r)
> > +		goto out;
> > +
> > +	kvm_x86_ops.cpuid_update(vcpu);
> >   out:
> >   	return r;
> >   }