s390: Recognize confidential-guest-support option

At least some s390 cpu models support "Protected Virtualization" (PV),
a mechanism to protect guests from eavesdropping by a compromised
hypervisor.

This is similar in function to other mechanisms like AMD's SEV and
POWER's PEF, which are controlled by the "confidential-guest-support"
machine option.  s390 is a slightly special case, because we already
supported PV, simply by using a CPU model with the required feature
(S390_FEAT_UNPACK).

To integrate this with the option used by other platforms, we
implement the following compromise:

 - When the confidential-guest-support option is set, s390 will
   recognize it, verify that the CPU can support PV (failing if not)
   and set virtio default options necessary for encrypted or protected
   guests, as on other platforms.  i.e. if confidential-guest-support
   is set, we will either create a guest capable of entering PV mode,
   or fail outright.

 - If confidential-guest-support is not set, guests might still be
   able to enter PV mode, if the CPU has the right model.  This may be
   a little surprising, but shouldn't actually be harmful.

To start a guest supporting Protected Virtualization using the new
option use the command line arguments:
    -object s390-pv-guest,id=pv0 -machine confidential-guest-support=pv0

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/docs/confidential-guest-support.txt b/docs/confidential-guest-support.txt
index 4da4c91bd37592e040e250c34de0fa07a528b2c8..71d07ba57af808b51c4a4d00fa54c3c423fd6237 100644 (file)
--- a/docs/confidential-guest-support.txt
+++ b/docs/confidential-guest-support.txt
@@ -43,4 +43,7 @@ AMD Secure Encrypted Virtualization (SEV)
 POWER Protected Execution Facility (PEF)
     docs/papr-pef.txt
 
+s390x Protected Virtualization (PV)
+    docs/system/s390x/protvirt.rst
+
 Other mechanisms may be supported in future.

diff --git a/docs/system/s390x/protvirt.rst b/docs/system/s390x/protvirt.rst
index 712974ad87b9e8565e326c268436492de547d284..0f481043d99e7cd4d8280bfdd2f2fa42d01aab08 100644 (file)
--- a/docs/system/s390x/protvirt.rst
+++ b/docs/system/s390x/protvirt.rst
@@ -22,15 +22,22 @@ If those requirements are met, the capability `KVM_CAP_S390_PROTECTED`
 will indicate that KVM can support PVMs on that LPAR.
 
 
-QEMU Settings
--------------
+Running a Protected Virtual Machine
+-----------------------------------
 
-To indicate to the VM that it can transition into protected mode, the
+To run a PVM you will need to select a CPU model which includes the
 `Unpack facility` (stfle bit 161 represented by the feature
-`unpack`/`S390_FEAT_UNPACK`) needs to be part of the cpu model of
-the VM.
+`unpack`/`S390_FEAT_UNPACK`), and add these options to the command line::
+
+    -object s390-pv-guest,id=pv0 \
+    -machine confidential-guest-support=pv0
+
+Adding these options will:
+
+* Ensure the `unpack` facility is available
+* Enable the IOMMU by default for all I/O devices
+* Initialize the PV mechanism
 
-All I/O devices need to use the IOMMU.
 Passthrough (vfio) devices are currently not supported.
 
 Host huge page backings are not supported. However guests can use huge

diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c
index ab3a2482aad73ed5faf32e49789a2ea7ff0d6e05..93eccfc05d5ddc4f6903dc71519f2448b9effb9b 100644 (file)
--- a/hw/s390x/pv.c
+++ b/hw/s390x/pv.c
@@ -14,8 +14,11 @@
 #include <linux/kvm.h>
 
 #include "cpu.h"
+#include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "sysemu/kvm.h"
+#include "qom/object_interfaces.h"
+#include "exec/confidential-guest-support.h"
 #include "hw/s390x/ipl.h"
 #include "hw/s390x/pv.h"
 
@@ -111,3 +114,62 @@ void s390_pv_inject_reset_error(CPUState *cs)
     /* Report that we are unable to enter protected mode */
     env->regs[r1 + 1] = DIAG_308_RC_INVAL_FOR_PV;
 }
+
+#define TYPE_S390_PV_GUEST "s390-pv-guest"
+OBJECT_DECLARE_SIMPLE_TYPE(S390PVGuest, S390_PV_GUEST)
+
+/**
+ * S390PVGuest:
+ *
+ * The S390PVGuest object is basically a dummy used to tell the
+ * confidential guest support system to use s390's PV mechanism.
+ *
+ * # $QEMU \
+ *         -object s390-pv-guest,id=pv0 \
+ *         -machine ...,confidential-guest-support=pv0
+ */
+struct S390PVGuest {
+    ConfidentialGuestSupport parent_obj;
+};
+
+typedef struct S390PVGuestClass S390PVGuestClass;
+
+struct S390PVGuestClass {
+    ConfidentialGuestSupportClass parent_class;
+};
+
+int s390_pv_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
+{
+    if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
+        return 0;
+    }
+
+    if (!s390_has_feat(S390_FEAT_UNPACK)) {
+        error_setg(errp,
+                   "CPU model does not support Protected Virtualization");
+        return -1;
+    }
+
+    cgs->ready = true;
+
+    return 0;
+}
+
+OBJECT_DEFINE_TYPE_WITH_INTERFACES(S390PVGuest,
+                                   s390_pv_guest,
+                                   S390_PV_GUEST,
+                                   CONFIDENTIAL_GUEST_SUPPORT,
+                                   { TYPE_USER_CREATABLE },
+                                   { NULL })
+
+static void s390_pv_guest_class_init(ObjectClass *oc, void *data)
+{
+}
+
+static void s390_pv_guest_init(Object *obj)
+{
+}
+
+static void s390_pv_guest_finalize(Object *obj)
+{
+}

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index a2d9a79c8493b762e8bb5d6753c773c90591836a..2972b607f364805c2b95fa88912b173fb5142861 100644 (file)
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -250,6 +250,9 @@ static void ccw_init(MachineState *machine)
     /* init CPUs (incl. CPU model) early so s390_has_feature() works */
     s390_init_cpus(machine);
 
+    /* Need CPU model to be determined before we can set up PV */
+    s390_pv_init(machine->cgs, &error_fatal);
+
     s390_flic_init();
 
     /* init the SIGP facility */

diff --git a/include/hw/s390x/pv.h b/include/hw/s390x/pv.h
index aee758bc2d34ba554789483fec7b3029df74b4c9..1f1f545bfc20231604b119783ef660b379821284 100644 (file)
--- a/include/hw/s390x/pv.h
+++ b/include/hw/s390x/pv.h
@@ -12,6 +12,9 @@
 #ifndef HW_S390_PV_H
 #define HW_S390_PV_H
 
+#include "qapi/error.h"
+#include "sysemu/kvm.h"
+
 #ifdef CONFIG_KVM
 #include "cpu.h"
 #include "hw/s390x/s390-virtio-ccw.h"
@@ -55,4 +58,18 @@ static inline void s390_pv_unshare(void) {}
 static inline void s390_pv_inject_reset_error(CPUState *cs) {};
 #endif /* CONFIG_KVM */
 
+int s390_pv_kvm_init(ConfidentialGuestSupport *cgs, Error **errp);
+static inline int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
+{
+    if (!cgs) {
+        return 0;
+    }
+    if (kvm_enabled()) {
+        return s390_pv_kvm_init(cgs, errp);
+    }
+
+    error_setg(errp, "Protected Virtualization requires KVM");
+    return -1;
+}
+
 #endif /* HW_S390_PV_H */