[PATCH v3 7/9] spapr: Add PEF based host trust limitation

[David Gibson <david@gibson.dropbear.id.au>]

Some upcoming POWER machines have a system called PEF (Protected
Execution Facility) which uses a small ultravisor to allow guests to
run in a way that they can't be eavesdropped by the hypervisor.  The
effect is roughly similar to AMD SEV, although the mechanisms are
quite different.

Most of the work of this is done between the guest, KVM and the
ultravisor, with little need for involvement by qemu.  However qemu
does need to tell KVM to allow secure VMs.

Because the availability of secure mode is a guest visible difference
which depends on having the right hardware and firmware, we don't
enable this by default.  In order to run a secure guest you need to
create a "pef-guest" object and set the host-trust-limitation machine
property to point to it.

Note that this just *allows* secure guests, the architecture of PEF is
such that the guest still needs to talk to the ultravisor to enter
secure mode.  Qemu has no directly way of knowing if the guest is in
secure mode, and certainly can't know until well after machine
creation time.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Ram Pai <linuxram@us.ibm.com>
---
 target/ppc/Makefile.objs |  2 +-
 target/ppc/pef.c         | 83 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 target/ppc/pef.c

diff --git a/target/ppc/Makefile.objs b/target/ppc/Makefile.objs
index e8fa18ce13..ac93b9700e 100644
--- a/target/ppc/Makefile.objs
+++ b/target/ppc/Makefile.objs
@@ -6,7 +6,7 @@ obj-y += machine.o mmu_helper.o mmu-hash32.o monitor.o arch_dump.o
 obj-$(TARGET_PPC64) += mmu-hash64.o mmu-book3s-v3.o compat.o
 obj-$(TARGET_PPC64) += mmu-radix64.o
 endif
-obj-$(CONFIG_KVM) += kvm.o
+obj-$(CONFIG_KVM) += kvm.o pef.o
 obj-$(call lnot,$(CONFIG_KVM)) += kvm-stub.o
 obj-y += dfp_helper.o
 obj-y += excp_helper.o
diff --git a/target/ppc/pef.c b/target/ppc/pef.c
new file mode 100644
index 0000000000..53a6af0347
--- /dev/null
+++ b/target/ppc/pef.c
@@ -0,0 +1,83 @@
+/*
+ * PEF (Protected Execution Facility) for POWER support
+ *
+ * Copyright David Gibson, Redhat Inc. 2020
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+#include "qom/object_interfaces.h"
+#include "sysemu/kvm.h"
+#include "migration/blocker.h"
+#include "exec/host-trust-limitation.h"
+
+#define TYPE_PEF_GUEST "pef-guest"
+#define PEF_GUEST(obj)                                  \
+    OBJECT_CHECK(PefGuestState, (obj), TYPE_PEF_GUEST)
+
+typedef struct PefGuestState PefGuestState;
+
+/**
+ * PefGuestState:
+ *
+ * The PefGuestState object is used for creating and managing a PEF
+ * guest.
+ *
+ * # $QEMU \
+ *         -object pef-guest,id=pef0 \
+ *         -machine ...,host-trust-limitation=pef0
+ */
+struct PefGuestState {
+    Object parent_obj;
+};
+
+static int pef_kvm_init(HostTrustLimitation *gmpo, Error **errp)
+{
+    if (!kvm_check_extension(kvm_state, KVM_CAP_PPC_SECURE_GUEST)) {
+        error_setg(errp,
+                   "KVM implementation does not support Secure VMs (is an ultravisor running?)");
+        return -1;
+    } else {
+        int ret = kvm_vm_enable_cap(kvm_state, KVM_CAP_PPC_SECURE_GUEST, 0, 1);
+
+        if (ret < 0) {
+            error_setg(errp,
+                       "Error enabling PEF with KVM");
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static void pef_guest_class_init(ObjectClass *oc, void *data)
+{
+    HostTrustLimitationClass *gmpc = HOST_TRUST_LIMITATION_CLASS(oc);
+
+    gmpc->kvm_init = pef_kvm_init;
+}
+
+static const TypeInfo pef_guest_info = {
+    .parent = TYPE_OBJECT,
+    .name = TYPE_PEF_GUEST,
+    .instance_size = sizeof(PefGuestState),
+    .class_init = pef_guest_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_HOST_TRUST_LIMITATION },
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+static void
+pef_register_types(void)
+{
+    type_register_static(&pef_guest_info);
+}
+
+type_init(pef_register_types);
-- 
2.26.2