Re: [PATCH v2 01/25] KVM: x86/mmu: avoid indirect call for get_cr3

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 3/8/22 17:32, Sean Christopherson wrote:
> Aha!  An idea that would provide line of sight to avoiding retpoline in all cases
> once we use static_call() for nested_ops, which I really want to do...  Drop the
> mmu hook entirely and replace it with:
>
> static inline kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu)
> {
> 	if (!mmu_is_nested(vcpu))
> 		return kvm_read_cr3(vcpu);
> 	else
> 		return kvm_x86_ops.nested_ops->get_guest_pgd(vcpu);
> }

Makes sense, but I think you mean

static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu,
						  struct kvm_mmu *mmu)
{
	if (unlikely(vcpu == &vcpu->arch.guest_mmu))
		return kvm_x86_ops.nested_ops->get_guest_pgd(vcpu);
	else
		return kvm_read_cr3(vcpu);
}

?

Paolo