On Tue, Nov 12, 2019 at 10:32:33PM -0800, Ram Pai wrote: > On Wed, Nov 13, 2019 at 11:14:27AM +1100, Paul Mackerras wrote: > > On Tue, Nov 12, 2019 at 06:45:55AM -0800, Ram Pai wrote: > > > On Tue, Nov 12, 2019 at 10:32:04PM +1100, Paul Mackerras wrote: > > > > On Mon, Nov 11, 2019 at 11:52:15PM -0800, Ram Pai wrote: > > > > > There is subtle problem removing that code from the assembly. > > > > > > > > > > If the H_SVM_INIT_ABORT hcall returns to the ultravisor without clearing > > > > > kvm->arch.secure_guest, the hypervisor will continue to think that the > > > > > VM is a secure VM. However the primary reason the H_SVM_INIT_ABORT > > > > > hcall was invoked, was to inform the Hypervisor that it should no longer > > > > > consider the VM as a Secure VM. So there is a inconsistency there. > > > > > > > > Most of the checks that look at whether a VM is a secure VM use code > > > > like "if (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE)". Now > > > > since KVMPPC_SECURE_INIT_ABORT is 4, an if statement such as that will > > > > take the false branch once we have set kvm->arch.secure_guest to > > > > KVMPPC_SECURE_INIT_ABORT in kvmppc_h_svm_init_abort. So in fact in > > > > most places we will treat the VM as a normal VM from then on. If > > > > there are any places where we still need to treat the VM as a secure > > > > VM while we are processing the abort we can easily do that too. > > > > > > Is the suggestion -- KVMPPC_SECURE_INIT_ABORT should never return back > > > to the Ultravisor? Because removing that assembly code will NOT lead the > > > > No. The suggestion is that vcpu->arch.secure_guest stays set to > > KVMPPC_SECURE_INIT_ABORT until userspace calls KVM_PPC_SVM_OFF. > > In the fast_guest_return path, if it finds > (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_ABORT) is true, should it return to > UV or not? > > Ideally it should return back to the ultravisor the first time > KVMPPC_SECURE_INIT_ABORT is set, and not than onwards. What is ideal about that behavior? Why would that be a particularly good thing to do? Paul.
