Re: [PATCH 5/8] KVM: nSVM: implement ondemand allocation of the nested state

Paolo Bonzini
2020-08-20T12:06:23Z

On 20/08/20 11:13, Maxim Levitsky wrote:
> @@ -3912,6 +3914,14 @@ static int svm_pre_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
> vmcb_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
>
> if (guest) {
> + /*
> + * This can happen if SVM was not enabled prior to #SMI,
> + * but guest corrupted the #SMI state and marked it as
> + * enabled it there
> + */
> + if (!svm->nested.initialized)
> + return 1;
> +
> if (kvm_vcpu_map(&svm->vcpu, gpa_to_gfn(vmcb_gpa), &map) == -EINVAL)
> return 1;

This can also happen if you live migrate while in SMM (EFER.SVME=0).
You need to check for the SVME bit in the SMM state save area, and:

1) triple fault if it is clear

2) call svm_allocate_nested if it is set.

Paolo