spapr: Add PEF based confidential guest support

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 confidential-guest-support
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 direct way of knowing if the guest is in
secure mode, and certainly can't know until well after machine
creation time.

To start a PEF-capable guest, use the command line options:
    -object pef-guest,id=pef0 -machine confidential-guest-support=pef0

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>

3 files changed, 141 insertions, 1 deletions

diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
index ffa2ec37fa..218631c883 100644
--- a/hw/ppc/meson.build
+++ b/hw/ppc/meson.build
@@ -27,6 +27,7 @@ ppc_ss.add(when: 'CONFIG_PSERIES', if_true: files(
   'spapr_nvdimm.c',
   'spapr_rtas_ddw.c',
   'spapr_numa.c',
+  'pef.c',
 ))
 ppc_ss.add(when: 'CONFIG_SPAPR_RNG', if_true: files('spapr_rng.c'))
 ppc_ss.add(when: ['CONFIG_PSERIES', 'CONFIG_LINUX'], if_true: files(
diff --git a/hw/ppc/pef.c b/hw/ppc/pef.c
new file mode 100644
index 0000000000..f9fd1f2a71
--- /dev/null
+++ b/hw/ppc/pef.c
@@ -0,0 +1,133 @@
+/*
+ * PEF (Protected Execution Facility) for POWER support
+ *
+ * Copyright Red Hat.
+ *
+ * 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/confidential-guest-support.h"
+#include "hw/ppc/pef.h"
+
+#define TYPE_PEF_GUEST "pef-guest"
+OBJECT_DECLARE_SIMPLE_TYPE(PefGuest, PEF_GUEST)
+
+typedef struct PefGuest PefGuest;
+typedef struct PefGuestClass PefGuestClass;
+
+struct PefGuestClass {
+    ConfidentialGuestSupportClass parent_class;
+};
+
+/**
+ * PefGuest:
+ *
+ * The PefGuest object is used for creating and managing a PEF
+ * guest.
+ *
+ * # $QEMU \
+ *         -object pef-guest,id=pef0 \
+ *         -machine ...,confidential-guest-support=pef0
+ */
+struct PefGuest {
+    ConfidentialGuestSupport parent_obj;
+};
+
+static int kvmppc_svm_init(Error **errp)
+{
+#ifdef CONFIG_KVM
+    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;
+#else
+    g_assert_not_reached();
+#endif
+}
+
+/*
+ * Don't set error if KVM_PPC_SVM_OFF ioctl is invoked on kernels
+ * that don't support this ioctl.
+ */
+static int kvmppc_svm_off(Error **errp)
+{
+#ifdef CONFIG_KVM
+    int rc;
+
+    rc = kvm_vm_ioctl(KVM_STATE(current_accel()), KVM_PPC_SVM_OFF);
+    if (rc && rc != -ENOTTY) {
+        error_setg_errno(errp, -rc, "KVM_PPC_SVM_OFF ioctl failed");
+        return rc;
+    }
+    return 0;
+#else
+    g_assert_not_reached();
+#endif
+}
+
+int pef_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
+{
+    if (!object_dynamic_cast(OBJECT(cgs), TYPE_PEF_GUEST)) {
+        return 0;
+    }
+
+    if (!kvm_enabled()) {
+        error_setg(errp, "PEF requires KVM");
+        return -1;
+    }
+
+    return kvmppc_svm_init(errp);
+}
+
+int pef_kvm_reset(ConfidentialGuestSupport *cgs, Error **errp)
+{
+    if (!object_dynamic_cast(OBJECT(cgs), TYPE_PEF_GUEST)) {
+        return 0;
+    }
+
+    /*
+     * If we don't have KVM we should never have been able to
+     * initialize PEF, so we should never get this far
+     */
+    assert(kvm_enabled());
+
+    return kvmppc_svm_off(errp);
+}
+
+OBJECT_DEFINE_TYPE_WITH_INTERFACES(PefGuest,
+                                   pef_guest,
+                                   PEF_GUEST,
+                                   CONFIDENTIAL_GUEST_SUPPORT,
+                                   { TYPE_USER_CREATABLE },
+                                   { NULL })
+
+static void pef_guest_class_init(ObjectClass *oc, void *data)
+{
+}
+
+static void pef_guest_init(Object *obj)
+{
+}
+
+static void pef_guest_finalize(Object *obj)
+{
+}
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 6c47466fc2..612356e9ec 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -83,6 +83,7 @@
 #include "hw/ppc/spapr_tpm_proxy.h"
 #include "hw/ppc/spapr_nvdimm.h"
 #include "hw/ppc/spapr_numa.h"
+#include "hw/ppc/pef.h"
 
 #include "monitor/monitor.h"
 
@@ -1574,7 +1575,7 @@ static void spapr_machine_reset(MachineState *machine)
     void *fdt;
     int rc;
 
-    kvmppc_svm_off(&error_fatal);
+    pef_kvm_reset(machine->cgs, &error_fatal);
     spapr_caps_apply(spapr);
 
     first_ppc_cpu = POWERPC_CPU(first_cpu);
@@ -2658,6 +2659,11 @@ static void spapr_machine_init(MachineState *machine)
     char *filename;
     Error *resize_hpt_err = NULL;
 
+    /*
+     * if Secure VM (PEF) support is configured, then initialize it
+     */
+    pef_kvm_init(machine->cgs, &error_fatal);
+
     msi_nonbroken = true;
 
     QLIST_INIT(&spapr->phbs);