KVM: PPC: Book3S HV: Add a capability for enabling secure guests

At present, on Power systems with Protected Execution Facility
hardware and an ultravisor, a KVM guest can transition to being a
secure guest at will.  Userspace (QEMU) has no way of knowing
whether a host system is capable of running secure guests.  This
will present a problem in future when the ultravisor is capable of
migrating secure guests from one host to another, because
virtualization management software will have no way to ensure that
secure guests only run in domains where all of the hosts can
support secure guests.

This adds a VM capability which has two functions: (a) userspace
can query it to find out whether the host can support secure guests,
and (b) userspace can enable it for a guest, which allows that
guest to become a secure guest.  If userspace does not enable it,
KVM will return an error when the ultravisor does the hypercall
that indicates that the guest is starting to transition to a
secure guest.  The ultravisor will then abort the transition and
the guest will terminate.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Ram Pai <linuxram@us.ibm.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 53b88cae3e73..6ed98e70097d 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -113,6 +113,15 @@ struct kvmppc_uvmem_page_pvt {
 	bool skip_page_out;
 };
 
+bool kvmppc_uvmem_available(void)
+{
+	/*
+	 * If kvmppc_uvmem_bitmap != NULL, then there is an ultravisor
+	 * and our data structures have been initialized successfully.
+	 */
+	return !!kvmppc_uvmem_bitmap;
+}
+
 int kvmppc_uvmem_slot_init(struct kvm *kvm, const struct kvm_memory_slot *slot)
 {
 	struct kvmppc_uvmem_slot *p;
@@ -218,6 +227,10 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
 	if (!kvm_is_radix(kvm))
 		return H_UNSUPPORTED;
 
+	/* NAK the transition to secure if not enabled */
+	if (!kvm->arch.svm_enabled)
+		return H_AUTHORITY;
+
 	srcu_idx = srcu_read_lock(&kvm->srcu);
 	slots = kvm_memslots(kvm);
 	kvm_for_each_memslot(memslot, slots) {