[PATCH RFC 04/12] vdpa: add vdpa simulator for block device

[Stefano Garzarella <sgarzare@redhat.com>]

From: Max Gurtovoy <mgurtovoy@nvidia.com>

This will allow running vDPA for virtio block protocol.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
[sgarzare: various cleanups/fixes]
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
v1:
- Removed unused headers
- Used cpu_to_vdpasim*() to store config fields
- Replaced 'select VDPA_SIM' with 'depends on VDPA_SIM' since selected
  option can not depend on other [Jason]
- Start with a single queue for now [Jason]
- Add comments to memory barriers
---
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 124 +++++++++++++++++++++++++++
 drivers/vdpa/Kconfig                 |   9 ++
 drivers/vdpa/vdpa_sim/Makefile       |   1 +
 3 files changed, 134 insertions(+)
 create mode 100644 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
new file mode 100644
index 000000000000..386dbb2f7138
--- /dev/null
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VDPA simulator for block device.
+ *
+ * Copyright (c) 2020, Mellanox Technologies. All rights reserved.
+ *
+ */
+
+#include <linux/module.h>
+
+#include "vdpa_sim.h"
+
+#define VDPASIM_BLK_FEATURES	((1ULL << VIRTIO_BLK_F_SIZE_MAX) | \
+				 (1ULL << VIRTIO_BLK_F_SEG_MAX)  | \
+				 (1ULL << VIRTIO_BLK_F_BLK_SIZE) | \
+				 (1ULL << VIRTIO_BLK_F_TOPOLOGY) | \
+				 (1ULL << VIRTIO_BLK_F_MQ))
+
+#define VDPASIM_BLK_CAPACITY 0x40000
+#define VDPASIM_BLK_SIZE_MAX 0x1000
+#define VDPASIM_BLK_SEG_MAX 32
+#define VDPASIM_BLK_VQ_NUM 1
+
+static struct vdpasim *vdpasim_blk_dev;
+
+static void vdpasim_blk_work(struct work_struct *work)
+{
+	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+	u8 status = VIRTIO_BLK_S_OK;
+	int i;
+
+	spin_lock(&vdpasim->lock);
+
+	if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
+		goto out;
+
+	for (i = 0; i < VDPASIM_BLK_VQ_NUM; i++) {
+		struct vdpasim_virtqueue *vq = &vdpasim->vqs[i];
+
+		if (!vq->ready)
+			continue;
+
+		while (vringh_getdesc_iotlb(&vq->vring, &vq->iov, &vq->iov,
+					    &vq->head, GFP_ATOMIC) > 0) {
+
+			int write;
+
+			vq->iov.i = vq->iov.used - 1;
+			write = vringh_iov_push_iotlb(&vq->vring, &vq->iov, &status, 1);
+			if (write <= 0)
+				break;
+
+			/* Make sure data is wrote before advancing index */
+			smp_wmb();
+
+			vringh_complete_iotlb(&vq->vring, vq->head, write);
+
+			/* Make sure used is visible before rasing the interrupt. */
+			smp_wmb();
+
+			if (vringh_need_notify_iotlb(&vq->vring) > 0)
+				vringh_notify(&vq->vring);
+
+			local_bh_disable();
+			if (vq->cb)
+				vq->cb(vq->private);
+			local_bh_enable();
+		}
+	}
+out:
+	spin_unlock(&vdpasim->lock);
+
+}
+
+static int __init vdpasim_blk_init(void)
+{
+	struct vdpasim_init_attr attr = {};
+	struct virtio_blk_config *config;
+	int ret;
+
+	attr.device_id = VIRTIO_ID_BLOCK;
+	attr.features = VDPASIM_FEATURES | VDPASIM_BLK_FEATURES;
+	attr.work_fn = vdpasim_blk_work;
+	vdpasim_blk_dev = vdpasim_create(&attr);
+	if (IS_ERR(vdpasim_blk_dev)) {
+		ret = PTR_ERR(vdpasim_blk_dev);
+		goto out;
+	}
+
+	config = (struct virtio_blk_config *)vdpasim_blk_dev->config;
+	config->capacity = cpu_to_vdpasim64(vdpasim_blk_dev, VDPASIM_BLK_CAPACITY);
+	config->size_max = cpu_to_vdpasim32(vdpasim_blk_dev, VDPASIM_BLK_SIZE_MAX);
+	config->seg_max = cpu_to_vdpasim32(vdpasim_blk_dev, VDPASIM_BLK_SEG_MAX);
+	config->num_queues = cpu_to_vdpasim16(vdpasim_blk_dev, VDPASIM_BLK_VQ_NUM);
+	config->min_io_size = cpu_to_vdpasim16(vdpasim_blk_dev, 1);
+	config->opt_io_size = cpu_to_vdpasim32(vdpasim_blk_dev, 1);
+	config->blk_size = cpu_to_vdpasim32(vdpasim_blk_dev, 512);
+
+	ret = vdpa_register_device(&vdpasim_blk_dev->vdpa);
+	if (ret)
+		goto put_dev;
+
+	return 0;
+
+put_dev:
+	put_device(&vdpasim_blk_dev->vdpa.dev);
+out:
+	return ret;
+}
+
+static void __exit vdpasim_blk_exit(void)
+{
+	struct vdpa_device *vdpa = &vdpasim_blk_dev->vdpa;
+
+	vdpa_unregister_device(vdpa);
+}
+
+module_init(vdpasim_blk_init)
+module_exit(vdpasim_blk_exit)
+
+MODULE_VERSION(DRV_VERSION);
+MODULE_LICENSE(DRV_LICENSE);
+MODULE_AUTHOR("Max Gurtovoy <mgurtovoy@nvidia.com>");
+MODULE_DESCRIPTION("vDPA Device Simulator for block device");
diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
index fdb1a9267347..0fb63362cd5d 100644
--- a/drivers/vdpa/Kconfig
+++ b/drivers/vdpa/Kconfig
@@ -24,6 +24,15 @@ config VDPA_SIM_NET
 	  to RX. This device is used for testing, prototyping and
 	  development of vDPA.
 
+config VDPA_SIM_BLOCK
+	tristate "vDPA simulator for block device"
+	depends on VDPA_SIM
+	default n
+	help
+	  vDPA block device simulator which terminates IO request in a
+	  memory buffer. This device is used for testing, prototyping and
+	  development of vDPA.
+
 config IFCVF
 	tristate "Intel IFC VF vDPA driver"
 	depends on PCI_MSI
diff --git a/drivers/vdpa/vdpa_sim/Makefile b/drivers/vdpa/vdpa_sim/Makefile
index 79d4536d347e..d458103302f2 100644
--- a/drivers/vdpa/vdpa_sim/Makefile
+++ b/drivers/vdpa/vdpa_sim/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_VDPA_SIM) += vdpa_sim.o
 obj-$(CONFIG_VDPA_SIM_NET) += vdpa_sim_net.o
+obj-$(CONFIG_VDPA_SIM_BLOCK) += vdpa_sim_blk.o
-- 
2.26.2