virtio: allow config read/write to fail

For vhost-user it's a protocol feature that can simply
be not supported. The subsequent patch introduces an extra
check that may cause config read/write to fail.

Change-Id: I5b0e11845fb6021472c608477f1797dada8ab961
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/417458
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>

include/spdk_internal/virtio.h

@@ -98,9 +98,9 @@ struct virtio_dev {
 };
 
 struct virtio_dev_ops {
-	void (*read_dev_cfg)(struct virtio_dev *hw, size_t offset,
+	int (*read_dev_cfg)(struct virtio_dev *hw, size_t offset,
 			    void *dst, int len);
-	void (*write_dev_cfg)(struct virtio_dev *hw, size_t offset,
+	int (*write_dev_cfg)(struct virtio_dev *hw, size_t offset,
 			     const void *src, int len);
 	uint8_t (*get_status)(struct virtio_dev *hw);
 	void (*set_status)(struct virtio_dev *hw, uint8_t status);
@@ -392,8 +392,9 @@ void virtio_dev_set_status(struct virtio_dev *vdev, uint8_t flag);
  * \param offset offset in bytes
  * \param src pointer to data to copy from
  * \param len length of data to copy in bytes
+ * \return 0 on success, negative errno otherwise
  */
-void virtio_dev_write_dev_config(struct virtio_dev *vdev, size_t offset, const void *src, int len);
+int virtio_dev_write_dev_config(struct virtio_dev *vdev, size_t offset, const void *src, int len);
 
 /**
  * Read raw data from the device config at given offset.  This call does not
@@ -403,8 +404,9 @@ void virtio_dev_write_dev_config(struct virtio_dev *vdev, size_t offset, const v
  * \param offset offset in bytes
  * \param dst pointer to buffer to copy data into
  * \param len length of data to copy in bytes
+ * \return 0 on success, negative errno otherwise
  */
-void virtio_dev_read_dev_config(struct virtio_dev *vdev, size_t offset, void *dst, int len);
+int virtio_dev_read_dev_config(struct virtio_dev *vdev, size_t offset, void *dst, int len);
 
 /**
  * Get backend-specific ops for given device.

lib/bdev/virtio/bdev_virtio_blk.c

@@ -352,8 +352,13 @@ virtio_blk_dev_init(struct virtio_blk_dev *bvdev, uint16_t max_queues)
 	int rc;
 
 	if (virtio_dev_has_feature(vdev, VIRTIO_BLK_F_BLK_SIZE)) {
-		virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, blk_size),
+		rc = virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, blk_size),
 						&block_size, sizeof(block_size));
+		if (rc) {
+			SPDK_ERRLOG("%s: config read failed: %s\n", vdev->name, spdk_strerror(-rc));
+			return rc;
+		}
+
 		if (block_size == 0 || block_size % 512 != 0) {
 			SPDK_ERRLOG("%s: invalid block size (%"PRIu32"). Must be "
 				    "a multiple of 512.\n", vdev->name, block_size);
@@ -363,8 +368,12 @@ virtio_blk_dev_init(struct virtio_blk_dev *bvdev, uint16_t max_queues)
 		block_size = 512;
 	}
 
-	virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, capacity),
+	rc = virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, capacity),
 					&capacity, sizeof(capacity));
+	if (rc) {
+		SPDK_ERRLOG("%s: config read failed: %s\n", vdev->name, spdk_strerror(-rc));
+		return rc;
+	}
 
 	/* `capacity` is a number of 512-byte sectors. */
 	num_blocks = capacity * 512 / block_size;
@@ -381,8 +390,12 @@ virtio_blk_dev_init(struct virtio_blk_dev *bvdev, uint16_t max_queues)
 	}
 
 	if (virtio_dev_has_feature(vdev, VIRTIO_BLK_F_MQ)) {
-		virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, num_queues),
+		rc = virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, num_queues),
 						&host_max_queues, sizeof(host_max_queues));
+		if (rc) {
+			SPDK_ERRLOG("%s: config read failed: %s\n", vdev->name, spdk_strerror(-rc));
+			return rc;
+		}
 	} else {
 		host_max_queues = 1;
 	}
@@ -478,8 +491,14 @@ virtio_pci_blk_dev_create(const char *name, struct virtio_pci_ctx *pci_ctx)
 
 	/* TODO: add a way to limit usable virtqueues */
 	if (virtio_dev_has_feature(vdev, VIRTIO_BLK_F_MQ)) {
-		virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, num_queues),
+		rc = virtio_dev_read_dev_config(vdev, offsetof(struct virtio_blk_config, num_queues),
 						&num_queues, sizeof(num_queues));
+		if (rc) {
+			SPDK_ERRLOG("%s: config read failed: %s\n", vdev->name, spdk_strerror(-rc));
+			virtio_dev_destruct(vdev);
+			free(bvdev);
+			return NULL;
+		}
 	} else {
 		num_queues = 1;
 	}

lib/bdev/virtio/bdev_virtio_scsi.c

@@ -337,8 +337,14 @@ virtio_pci_scsi_dev_create(const char *name, struct virtio_pci_ctx *pci_ctx)
 		return NULL;
 	}
 
-	virtio_dev_read_dev_config(vdev, offsetof(struct virtio_scsi_config, num_queues),
+	rc = virtio_dev_read_dev_config(vdev, offsetof(struct virtio_scsi_config, num_queues),
 					&num_queues, sizeof(num_queues));
+	if (rc) {
+		SPDK_ERRLOG("%s: config read failed: %s\n", vdev->name, spdk_strerror(-rc));
+		virtio_dev_destruct(vdev);
+		free(svdev);
+		return NULL;
+	}
 
 	rc = virtio_scsi_dev_init(svdev, num_queues);
 	if (rc != 0) {

lib/virtio/virtio.c

@@ -683,18 +683,18 @@ virtio_dev_release_queue(struct virtio_dev *vdev, uint16_t index)
 	pthread_mutex_unlock(&vdev->mutex);
 }
 
-void
+int
 virtio_dev_read_dev_config(struct virtio_dev *dev, size_t offset,
 			   void *dst, int length)
 {
-	virtio_dev_backend_ops(dev)->read_dev_cfg(dev, offset, dst, length);
+	return virtio_dev_backend_ops(dev)->read_dev_cfg(dev, offset, dst, length);
 }
 
-void
+int
 virtio_dev_write_dev_config(struct virtio_dev *dev, size_t offset,
 			    const void *src, int length)
 {
-	virtio_dev_backend_ops(dev)->write_dev_cfg(dev, offset, src, length);
+	return virtio_dev_backend_ops(dev)->write_dev_cfg(dev, offset, src, length);
 }
 
 void

lib/virtio/virtio_pci.c

@@ -146,7 +146,7 @@ io_write64_twopart(uint64_t val, uint32_t *lo, uint32_t *hi)
 	spdk_mmio_write_4(hi, val >> 32);
 }
 
-static void
+static int
 modern_read_dev_config(struct virtio_dev *dev, size_t offset,
 		       void *dst, int length)
 {
@@ -165,9 +165,11 @@ modern_read_dev_config(struct virtio_dev *dev, size_t offset,
 
 		new_gen = spdk_mmio_read_1(&hw->common_cfg->config_generation);
 	} while (old_gen != new_gen);
+
+	return 0;
 }
 
-static void
+static int
 modern_write_dev_config(struct virtio_dev *dev, size_t offset,
 			const void *src, int length)
 {
@@ -178,6 +180,8 @@ modern_write_dev_config(struct virtio_dev *dev, size_t offset,
 	for (i = 0;  i < length; i++) {
 		spdk_mmio_write_1(((uint8_t *)hw->dev_cfg) + offset + i, *p++);
 	}
+
+	return 0;
 }
 
 static uint64_t

lib/virtio/virtio_user.c

@@ -215,7 +215,7 @@ virtio_user_dev_setup(struct virtio_dev *vdev)
 	return 0;
 }
 
-static void
+static int
 virtio_user_read_dev_config(struct virtio_dev *vdev, size_t offset,
 			    void *dst, int length)
 {
@@ -227,13 +227,14 @@ virtio_user_read_dev_config(struct virtio_dev *vdev, size_t offset,
 
 	if (dev->ops->send_request(dev, VHOST_USER_GET_CONFIG, &cfg) < 0) {
 		SPDK_ERRLOG("get_config failed: %s\n", spdk_strerror(errno));
-		return;
+		return -errno;
 	}
 
 	memcpy(dst, cfg.region + offset, length);
+	return 0;
 }
 
-static void
+static int
 virtio_user_write_dev_config(struct virtio_dev *vdev, size_t offset,
 			     const void *src, int length)
 {
@@ -246,8 +247,10 @@ virtio_user_write_dev_config(struct virtio_dev *vdev, size_t offset,
 
 	if (dev->ops->send_request(dev, VHOST_USER_SET_CONFIG, &cfg) < 0) {
 		SPDK_ERRLOG("set_config failed: %s\n", spdk_strerror(errno));
-		return;
+		return -errno;
 	}
+
+	return 0;
 }
 
 static void