[Qemu-devel] [PATCH] virtio: Introduce virtio-testdev

[Andrew Jones]

This is a virtio version of hw/misc/debugexit and should evolve into a
virtio version of pc-testdev. pc-testdev uses the PC's ISA bus, whereas
this testdev can be plugged into a virtio-mmio transport, which is
needed for kvm-unit-tests/arm. virtio-testdev uses the virtio device
config space as a communication channel, and implements an RTAS-like
protocol through it allowing guests to execute commands. Only three
commands are currently implemented;
1) VERSION: for version compatibility checks
2) CLEAR:   set all the config space back to zero
3) EXIT:    exit() from qemu with a status code

Note, the protocol also requires all data passing through the config
space to be in little-endian.

See [1] for an example of a driver for this device.

[1] 
https://github.com/rhdrjones/kvm-unit-tests/blob/ff8df5378ffccfbdf25fe79241837e61eb2258e1/lib/virtio-testdev.c

Signed-off-by: Andrew Jones <address@hidden>
---
 default-configs/arm-softmmu.mak |   2 +
 hw/virtio/Makefile.objs         |   1 +
 hw/virtio/virtio-testdev.c      | 117 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 120 insertions(+)
 create mode 100644 hw/virtio/virtio-testdev.c

diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
index ac0815d66310f..56f8086e61974 100644
--- a/default-configs/arm-softmmu.mak
+++ b/default-configs/arm-softmmu.mak
@@ -80,3 +80,5 @@ CONFIG_VERSATILE_PCI=y
 CONFIG_VERSATILE_I2C=y
 
 CONFIG_SDHCI=y
+
+CONFIG_VIRTIO_TESTDEV=y
diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
index 1ba53d9cc316c..b3d16d522f54b 100644
--- a/hw/virtio/Makefile.objs
+++ b/hw/virtio/Makefile.objs
@@ -3,6 +3,7 @@ common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
 common-obj-y += virtio-bus.o
 common-obj-y += virtio-mmio.o
 common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += dataplane/
+common-obj-$(CONFIG_VIRTIO_TESTDEV) += virtio-testdev.o
 
 obj-y += virtio.o virtio-balloon.o 
 obj-$(CONFIG_LINUX) += vhost.o
diff --git a/hw/virtio/virtio-testdev.c b/hw/virtio/virtio-testdev.c
new file mode 100644
index 0000000000000..d6852d563702e
--- /dev/null
+++ b/hw/virtio/virtio-testdev.c
@@ -0,0 +1,117 @@
+#include "hw/virtio/virtio-bus.h"
+
+#define VIRTIO_ID_TESTDEV 0xffff
+
+#define TYPE_VIRTIO_TESTDEV "virtio-testdev"
+#define VIRTIO_TESTDEV(obj) \
+        OBJECT_CHECK(VirtIOTestdev, (obj), TYPE_VIRTIO_TESTDEV)
+
+#define TESTDEV_MAJOR_VER 1
+#define TESTDEV_MINOR_VER 1
+
+#define CONFIG_SIZE 0x100
+
+enum {
+    VERSION = 1,
+    CLEAR,
+    EXIT,
+};
+
+enum { TOKEN, NARGS, NRETS, ARG1, ARG2, ARG3, ARG4, };
+
+#define RET1(nargs) (ARG1 + (nargs) + 0)
+#define RET2(nargs) (ARG1 + (nargs) + 1)
+#define RET3(nargs) (ARG1 + (nargs) + 2)
+#define RET4(nargs) (ARG1 + (nargs) + 3)
+
+#define calc_len(nargs, nrets) ((3 + (nargs) + (nrets)) * 4)
+
+typedef struct VirtIOTestdev {
+    VirtIODevice parent_obj;
+    uint8_t config[CONFIG_SIZE];
+    size_t len; /* currently used bytes */
+} VirtIOTestdev;
+
+static void virtio_testdev_get_config(VirtIODevice *vdev, uint8_t *config_data)
+{
+    VirtIOTestdev *dev = VIRTIO_TESTDEV(vdev);
+    memcpy(config_data, &dev->config[0], dev->len);
+}
+
+static void virtio_testdev_set_config(VirtIODevice *vdev,
+                                      const uint8_t *config_data)
+{
+    VirtIOTestdev *dev = VIRTIO_TESTDEV(vdev);
+    uint32_t *c32 = (uint32_t *)&dev->config[0];
+    uint32_t token, nargs, nrets;
+
+    memcpy(c32, config_data, 32); /* assume write is in first 32 bytes,
+                                     we can grab more later, if needed */
+    token = le32_to_cpu(c32[TOKEN]);
+    nargs = le32_to_cpu(c32[NARGS]);
+    nrets = le32_to_cpu(c32[NRETS]);
+
+    if (!token) {
+        return;
+    }
+
+    switch (token) {
+    case VERSION:
+        c32[RET1(nargs)] =
+            cpu_to_le32((TESTDEV_MAJOR_VER << 16) | TESTDEV_MINOR_VER);
+        break;
+    case CLEAR:
+        memset(c32, 0, CONFIG_SIZE);
+        break;
+    case EXIT:
+        exit((le32_to_cpu(c32[ARG1]) << 1) | 1);
+    default:
+        break;
+    }
+
+    c32[TOKEN] = 0;
+    dev->len = calc_len(nargs, nrets);
+}
+
+static uint32_t virtio_testdev_get_features(VirtIODevice *vdev, uint32_t f)
+{
+    return f;
+}
+
+static int virtio_testdev_init(VirtIODevice *vdev)
+{
+    virtio_init(vdev, "virtio-testdev", VIRTIO_ID_TESTDEV, CONFIG_SIZE);
+    return 0;
+}
+
+static int virtio_testdev_exit(DeviceState *qdev)
+{
+    virtio_cleanup(VIRTIO_DEVICE(qdev));
+    return 0;
+}
+
+static void virtio_testdev_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+    dc->exit = virtio_testdev_exit;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+    vdc->init = virtio_testdev_init;
+    vdc->get_config = virtio_testdev_get_config;
+    vdc->set_config = virtio_testdev_set_config;
+    vdc->get_features = virtio_testdev_get_features;
+}
+
+static const TypeInfo virtio_testdev_info = {
+    .name = TYPE_VIRTIO_TESTDEV,
+    .parent = TYPE_VIRTIO_DEVICE,
+    .instance_size = sizeof(VirtIOTestdev),
+    .class_init = virtio_testdev_class_init,
+};
+
+static void virtio_register_types(void)
+{
+    type_register_static(&virtio_testdev_info);
+}
+
+type_init(virtio_register_types)
-- 
1.8.3.1