s390x/virtio-ccw: add virtio set-revision call

Handle the virtio-ccw revision according to what the guest sets.
When revision 1 is selected, we have a virtio-1 standard device
with byteswapping for the virtio rings.

When a channel gets disabled, we have to revert to the legacy behavior
in case the next user of the device does not negotiate the revision 1
anymore (e.g. the boot firmware uses revision 1, but the operating
system only uses the legacy mode).

Note that revisions > 0 are still disabled.

[CH: assure memory accesses are always BE]
Signed-off-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>

hw/s390x/virtio-ccw.c

@@ -21,6 +21,7 @@
 #include "hw/sysbus.h"
 #include "qemu/bitops.h"
 #include "qemu/error-report.h"
+#include "hw/virtio/virtio-access.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/s390x/adapter.h"
 #include "hw/s390x/s390_flic.h"
@@ -261,6 +262,12 @@ typedef struct VirtioThinintInfo {
     uint8_t isc;
 } QEMU_PACKED VirtioThinintInfo;
 
+typedef struct VirtioRevInfo {
+    uint16_t revision;
+    uint16_t length;
+    uint8_t data[0];
+} QEMU_PACKED VirtioRevInfo;
+
 /* Specify where the virtqueues for the subchannel are in guest memory. */
 static int virtio_ccw_set_vqs(SubchDev *sch, uint64_t addr, uint32_t align,
                               uint16_t index, uint16_t num)
@@ -319,6 +326,7 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
 {
     int ret;
     VqInfoBlock info;
+    VirtioRevInfo revinfo;
     uint8_t status;
     VirtioFeatDesc features;
     void *config;
@@ -401,7 +409,16 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
                                                 MEMTXATTRS_UNSPECIFIED,
                                                 NULL);
             if (features.index == 0) {
-                features.features = vdev->host_features;
+                features.features = (uint32_t)vdev->host_features;
+            } else if (features.index == 1) {
+                features.features = (uint32_t)(vdev->host_features >> 32);
+                /*
+                 * Don't offer version 1 to the guest if it did not
+                 * negotiate at least revision 1.
+                 */
+                if (dev->revision <= 0) {
+                    features.features &= ~(1 << (VIRTIO_F_VERSION_1 - 32));
+                }
             } else {
                 /* Return zeroes if the guest supports more feature bits. */
                 features.features = 0;
@@ -437,7 +454,20 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
                                                      MEMTXATTRS_UNSPECIFIED,
                                                      NULL);
             if (features.index == 0) {
-                virtio_set_features(vdev, features.features);
+                virtio_set_features(vdev,
+                                    (vdev->guest_features & 0xffffffff00000000ULL) |
+                                    features.features);
+            } else if (features.index == 1) {
+                /*
+                 * The guest should not set version 1 if it didn't
+                 * negotiate a revision >= 1.
+                 */
+                if (dev->revision <= 0) {
+                    features.features &= ~(1 << (VIRTIO_F_VERSION_1 - 32));
+                }
+                virtio_set_features(vdev,
+                                    (vdev->guest_features & 0x00000000ffffffffULL) |
+                                    ((uint64_t)features.features << 32));
             } else {
                 /*
                  * If the guest supports more feature bits, assert that it
@@ -658,6 +688,40 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
             }
         }
         break;
+    case CCW_CMD_SET_VIRTIO_REV:
+        len = sizeof(revinfo);
+        if (ccw.count < len) {
+            ret = -EINVAL;
+            break;
+        }
+        if (!ccw.cda) {
+            ret = -EFAULT;
+            break;
+        }
+        revinfo.revision =
+            address_space_lduw_be(&address_space_memory, ccw.cda,
+                                  MEMTXATTRS_UNSPECIFIED, NULL);
+        revinfo.length =
+            address_space_lduw_be(&address_space_memory,
+                                  ccw.cda + sizeof(revinfo.revision),
+                                  MEMTXATTRS_UNSPECIFIED, NULL);
+        if (ccw.count < len + revinfo.length ||
+            (check_len && ccw.count > len + revinfo.length)) {
+            ret = -EINVAL;
+            break;
+        }
+        /*
+         * Once we start to support revisions with additional data, we'll
+         * need to fetch it here. Nothing to do for now, though.
+         */
+        if (dev->revision >= 0 ||
+            revinfo.revision > virtio_ccw_rev_max(vdev)) {
+            ret = -ENOSYS;
+            break;
+        }
+        ret = 0;
+        dev->revision = revinfo.revision;
+        break;
     default:
         ret = -ENOSYS;
         break;
@@ -665,6 +729,13 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
     return ret;
 }
 
+static void virtio_sch_disable_cb(SubchDev *sch)
+{
+    VirtioCcwDevice *dev = sch->driver_data;
+
+    dev->revision = -1;
+}
+
 static void virtio_ccw_device_realize(VirtioCcwDevice *dev, Error **errp)
 {
     unsigned int cssid = 0;
@@ -784,12 +855,15 @@ static void virtio_ccw_device_realize(VirtioCcwDevice *dev, Error **errp)
     css_sch_build_virtual_schib(sch, 0, VIRTIO_CCW_CHPID_TYPE);
 
     sch->ccw_cb = virtio_ccw_cb;
+    sch->disable_cb = virtio_sch_disable_cb;
 
     /* Build senseid data. */
     memset(&sch->id, 0, sizeof(SenseId));
     sch->id.reserved = 0xff;
     sch->id.cu_type = VIRTIO_CCW_CU_TYPE;
 
+    dev->revision = -1;
+
     if (k->realize) {
         k->realize(dev, &err);
     }

hw/s390x/virtio-ccw.h

@@ -41,6 +41,7 @@
 #define CCW_CMD_SET_CONF_IND 0x53
 #define CCW_CMD_READ_VQ_CONF 0x32
 #define CCW_CMD_SET_IND_ADAPTER 0x73
+#define CCW_CMD_SET_VIRTIO_REV 0x83
 
 #define TYPE_VIRTIO_CCW_DEVICE "virtio-ccw-device"
 #define VIRTIO_CCW_DEVICE(obj) \
@@ -86,6 +87,7 @@ struct VirtioCcwDevice {
     DeviceState parent_obj;
     SubchDev *sch;
     char *bus_id;
+    int revision;
     VirtioBusState bus;
     bool ioeventfd_started;
     bool ioeventfd_disabled;
@@ -99,6 +101,12 @@ struct VirtioCcwDevice {
     uint64_t ind_bit;
 };
 
+/* The maximum virtio revision we support. */
+static inline int virtio_ccw_rev_max(VirtIODevice *vdev)
+{
+    return 0;
+}
+
 /* virtual css bus type */
 typedef struct VirtualCssBus {
     BusState parent_obj;