[PATCH v4 11/14] 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.

It's a preliminary implementation with a simple request handling:
for each request, only the status (last byte) is set.
It's always set to VIRTIO_BLK_S_OK.

Also input validation is missing and will be added in the next commits.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
[sgarzare: various cleanups/fixes]
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
v4:
- include linux/blkdev.h to fix a build issue
- fix vdpa_register_device() passing the new 'nvqs' params

v3:
- updated Mellanox copyright to NVIDIA [Max]
- explained in the commit message that inputs are validated in subsequent
  patches [Stefan]

v2:
- rebased on top of other changes (dev_attr, get_config(), notify(), etc.)
- memset to 0 the config structure in vdpasim_blk_get_config()
- used vdpasim pointer in vdpasim_blk_get_config()

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 | 145 +++++++++++++++++++++++++++
 drivers/vdpa/Kconfig                 |   7 ++
 drivers/vdpa/vdpa_sim/Makefile       |   1 +
 3 files changed, 153 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..64926a70af5e
--- /dev/null
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VDPA simulator for block device.
+ *
+ * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/blkdev.h>
+#include <linux/vringh.h>
+#include <linux/vdpa.h>
+#include <uapi/linux/virtio_blk.h>
+
+#include "vdpa_sim.h"
+
+#define DRV_VERSION  "0.1"
+#define DRV_AUTHOR   "Max Gurtovoy <mgurtovoy@nvidia.com>"
+#define DRV_DESC     "vDPA Device Simulator for block device"
+#define DRV_LICENSE  "GPL v2"
+
+#define VDPASIM_BLK_FEATURES	(VDPASIM_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->out_iov,
+					    &vq->in_iov, &vq->head,
+					    GFP_ATOMIC) > 0) {
+			int write;
+
+			vq->in_iov.i = vq->in_iov.used - 1;
+			write = vringh_iov_push_iotlb(&vq->vring, &vq->in_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();
+
+			local_bh_disable();
+			if (vringh_need_notify_iotlb(&vq->vring) > 0)
+				vringh_notify(&vq->vring);
+			local_bh_enable();
+		}
+	}
+out:
+	spin_unlock(&vdpasim->lock);
+}
+
+static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
+{
+	struct virtio_blk_config *blk_config = config;
+
+	memset(config, 0, sizeof(struct virtio_blk_config));
+
+	blk_config->capacity = cpu_to_vdpasim64(vdpasim, VDPASIM_BLK_CAPACITY);
+	blk_config->size_max = cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_SIZE_MAX);
+	blk_config->seg_max = cpu_to_vdpasim32(vdpasim, VDPASIM_BLK_SEG_MAX);
+	blk_config->num_queues = cpu_to_vdpasim16(vdpasim, VDPASIM_BLK_VQ_NUM);
+	blk_config->min_io_size = cpu_to_vdpasim16(vdpasim, 1);
+	blk_config->opt_io_size = cpu_to_vdpasim32(vdpasim, 1);
+	blk_config->blk_size = cpu_to_vdpasim32(vdpasim, SECTOR_SIZE);
+}
+
+static int __init vdpasim_blk_init(void)
+{
+	struct vdpasim_dev_attr dev_attr = {};
+	int ret;
+
+	dev_attr.id = VIRTIO_ID_BLOCK;
+	dev_attr.supported_features = VDPASIM_BLK_FEATURES;
+	dev_attr.nvqs = VDPASIM_BLK_VQ_NUM;
+	dev_attr.config_size = sizeof(struct virtio_blk_config);
+	dev_attr.get_config = vdpasim_blk_get_config;
+	dev_attr.work_fn = vdpasim_blk_work;
+	dev_attr.buffer_size = PAGE_SIZE;
+
+	vdpasim_blk_dev = vdpasim_create(&dev_attr);
+	if (IS_ERR(vdpasim_blk_dev)) {
+		ret = PTR_ERR(vdpasim_blk_dev);
+		goto out;
+	}
+
+	ret = vdpa_register_device(&vdpasim_blk_dev->vdpa, VDPASIM_BLK_VQ_NUM);
+	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(DRV_AUTHOR);
+MODULE_DESCRIPTION(DRV_DESC);
diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
index 6e82a0e228c2..a503c1b2bfd9 100644
--- a/drivers/vdpa/Kconfig
+++ b/drivers/vdpa/Kconfig
@@ -26,6 +26,13 @@ config VDPA_SIM_NET
 	help
 	  vDPA networking device simulator which loops TX traffic back to RX.
 
+config VDPA_SIM_BLOCK
+	tristate "vDPA simulator for block device"
+	depends on VDPA_SIM
+	help
+	  vDPA block device simulator which terminates IO request in a
+	  memory buffer.
+
 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
-- 
2.30.2