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From:   Kishon Vijay Abraham I <kishon@ti.com>
To:     Ohad Ben-Cohen <ohad@wizery.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Jon Mason <jdmason@kudzu.us>,
        Dave Jiang <dave.jiang@intel.com>,
        Allen Hubbe <allenbh@gmail.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>
CC:     <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-remoteproc@vger.kernel.org>, <linux-ntb@googlegroups.com>,
        <linux-pci@vger.kernel.org>, <kvm@vger.kernel.org>,
        <virtualization@lists.linux-foundation.org>,
        <netdev@vger.kernel.org>
Subject: [RFC PATCH 18/22] virtio_pci: Add VIRTIO driver for VHOST on Configurable PCIe Endpoint device
Date:   Thu, 2 Jul 2020 13:51:39 +0530
Message-ID: <20200702082143.25259-19-kishon@ti.com>
In-Reply-To: <20200702082143.25259-1-kishon@ti.com>
References: <20200702082143.25259-1-kishon@ti.com>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add VIRTIO driver to support Linux VHOST on Configurable PCIe Endpoint
device in the backend.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
---
 drivers/virtio/Kconfig          |   9 +
 drivers/virtio/Makefile         |   1 +
 drivers/virtio/virtio_pci_epf.c | 670 ++++++++++++++++++++++++++++++++
 include/linux/virtio.h          |   3 +
 4 files changed, 683 insertions(+)
 create mode 100644 drivers/virtio/virtio_pci_epf.c

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 69a32dfc318a..4b251f8482ae 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -43,6 +43,15 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_PCI_EPF
+	bool "Support for virtio device on configurable PCIe Endpoint"
+	depends on VIRTIO_PCI
+	help
+          Select this configuration option to enable the VIRTIO driver
+          for configurable PCIe Endpoint running Linux in backend.
+
+          If in doubt, say "N" to disable VIRTIO PCI EPF driver.
+
 config VIRTIO_VDPA
 	tristate "vDPA driver for virtio devices"
 	depends on VDPA
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 29a1386ecc03..08a158365d5e 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_VIRTIO_MMIO) += virtio_mmio.o
 obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o
 virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
+virtio_pci-$(CONFIG_VIRTIO_PCI_EPF) += virtio_pci_epf.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
 obj-$(CONFIG_VIRTIO_VDPA) += virtio_vdpa.o
diff --git a/drivers/virtio/virtio_pci_epf.c b/drivers/virtio/virtio_pci_epf.c
new file mode 100644
index 000000000000..20e53869f179
--- /dev/null
+++ b/drivers/virtio/virtio_pci_epf.c
@@ -0,0 +1,670 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * Virtio PCI driver - Configurable PCIe Endpoint device Support
+ *
+ * The Configurable PCIe Endpoint device is present on an another system running
+ * Linux and configured using drivers/pci/endpoint/functions/pci-epf-vhost.c
+ *
+ * Copyright (C) 2020 Texas Instruments
+ * Author: Kishon Vijay Abraham I <kishon@ti.com>
+ */
+
+#include <linux/delay.h>
+#include "virtio_pci_common.h"
+
+#define DRV_MODULE_NAME		"virtio-pci-epf"
+
+#define HOST_FEATURES_LOWER	0x00
+#define HOST_FEATURES_UPPER	0x04
+#define GUEST_FEATURES_LOWER	0x08
+#define GUEST_FEATURES_UPPER	0x0C
+#define MSIX_CONFIG		0x10
+#define NUM_QUEUES		0x12
+#define DEVICE_STATUS		0x14
+#define CONFIG_GENERATION	0x15
+#define ISR			0x16
+#define HOST_CMD		0x1A
+enum host_cmd {
+	HOST_CMD_NONE,
+	HOST_CMD_SET_STATUS,
+	HOST_CMD_FINALIZE_FEATURES,
+	HOST_CMD_RESET,
+};
+
+#define HOST_CMD_STATUS		0x1B
+enum host_cmd_status {
+	HOST_CMD_STATUS_NONE,
+	HOST_CMD_STATUS_OKAY,
+	HOST_CMD_STATUS_ERROR,
+};
+
+#define QUEUE_BASE		0x1C
+#define CMD			0x00
+enum queue_cmd {
+	QUEUE_CMD_NONE,
+	QUEUE_CMD_ACTIVATE,
+	QUEUE_CMD_DEACTIVATE,
+	QUEUE_CMD_NOTIFY,
+};
+
+#define CMD_STATUS		0x01
+enum queue_cmd_status {
+	QUEUE_CMD_STATUS_NONE,
+	QUEUE_CMD_STATUS_OKAY,
+	QUEUE_CMD_STATUS_ERROR,
+};
+
+#define STATUS			0x2
+#define STATUS_ACTIVE		BIT(0)
+
+#define NUM_BUFFERS		0x04
+#define MSIX_VECTOR		0x06
+#define ADDR_LOWER		0x08
+#define ADDR_UPPER		0x0C
+#define QUEUE_CMD(n)		(QUEUE_BASE + CMD + (n) * 16)
+#define QUEUE_CMD_STATUS(n)	(QUEUE_BASE + CMD_STATUS + (n) * 16)
+#define QUEUE_STATUS(n)		(QUEUE_BASE + STATUS + (n) * 16)
+#define QUEUE_NUM_BUFFERS(n)	(QUEUE_BASE + NUM_BUFFERS + (n) * 16)
+#define QUEUE_MSIX_VECTOR(n)	(QUEUE_BASE + MSIX_VECTOR + (n) * 16)
+#define QUEUE_ADDR_LOWER(n)	(QUEUE_BASE + ADDR_LOWER + (n) * 16)
+#define QUEUE_ADDR_UPPER(n)	(QUEUE_BASE + ADDR_UPPER + (n) * 16)
+
+#define DEVICE_CFG_SPACE	0x110
+
+#define COMMAND_TIMEOUT	1000 /* 1 Sec */
+
+struct virtio_pci_epf {
+	/* mutex to protect sending commands to EPF vhost */
+	struct mutex lock;
+	struct virtio_pci_device vp_dev;
+};
+
+#define to_virtio_pci_epf(dev) container_of((dev), struct virtio_pci_epf, vp_dev)
+
+/* virtio_pci_epf_send_command - Send commands to the remote EPF device running
+ *   vhost driver
+ * @vp_dev: Virtio PCIe device that communicates with the endpoint device
+ * @command: The command that has to be sent to the remote endpoint device
+ *
+ * Helper function to send commands to the remote endpoint function device
+ * running vhost driver.
+ */
+static int virtio_pci_epf_send_command(struct virtio_pci_device *vp_dev,
+				       u32 command)
+{
+	struct virtio_pci_epf *pci_epf;
+	void __iomem *ioaddr;
+	ktime_t timeout;
+	bool timedout;
+	int ret = 0;
+	u8 status;
+
+	pci_epf = to_virtio_pci_epf(vp_dev);
+	ioaddr = vp_dev->ioaddr;
+
+	mutex_lock(&pci_epf->lock);
+	writeb(command, ioaddr + HOST_CMD);
+	timeout = ktime_add_ms(ktime_get(), COMMAND_TIMEOUT);
+	while (1) {
+		timedout = ktime_after(ktime_get(), timeout);
+		status = readb(ioaddr + HOST_CMD_STATUS);
+
+		if (status == HOST_CMD_STATUS_ERROR) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if (status == HOST_CMD_STATUS_OKAY)
+			break;
+
+		if (WARN_ON(timedout)) {
+			ret = -ETIMEDOUT;
+			break;
+		}
+
+		usleep_range(5, 10);
+	}
+
+	writeb(HOST_CMD_STATUS_NONE, ioaddr + HOST_CMD_STATUS);
+	mutex_unlock(&pci_epf->lock);
+
+	return ret;
+}
+
+/* virtio_pci_epf_send_queue_command - Send commands to the remote EPF device
+ *   for configuring virtqueue
+ * @vp_dev: Virtio PCIe device that communicates with the endpoint device
+ * @vq: The virtqueue that has to be configured on the remote endpoint device
+ * @command: The command that has to be sent to the remote endpoint device
+ *
+ * Helper function to send commands to the remote endpoint function device for
+ * configuring the virtqueue.
+ */
+static int virtio_pci_epf_send_queue_command(struct virtio_pci_device *vp_dev,
+					     struct virtqueue *vq, u8 command)
+{
+	void __iomem *ioaddr;
+	ktime_t timeout;
+	bool timedout;
+	int ret = 0;
+	u8 status;
+
+	ioaddr = vp_dev->ioaddr;
+
+	mutex_lock(&vq->lock);
+	writeb(command, ioaddr + QUEUE_CMD(vq->index));
+	timeout = ktime_add_ms(ktime_get(), COMMAND_TIMEOUT);
+	while (1) {
+		timedout = ktime_after(ktime_get(), timeout);
+		status = readb(ioaddr + QUEUE_CMD_STATUS(vq->index));
+
+		if (status == QUEUE_CMD_STATUS_ERROR) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if (status == QUEUE_CMD_STATUS_OKAY)
+			break;
+
+		if (WARN_ON(timedout)) {
+			ret = -ETIMEDOUT;
+			break;
+		}
+
+		usleep_range(5, 10);
+	}
+
+	writeb(QUEUE_CMD_STATUS_NONE, ioaddr + QUEUE_CMD_STATUS(vq->index));
+	mutex_unlock(&vq->lock);
+
+	return ret;
+}
+
+/* virtio_pci_epf_get_features - virtio_config_ops to get EPF vhost device
+ *   features
+ * @vdev: Virtio device that communicates with the remote EPF vhost device
+ *
+ * virtio_config_ops to get EPF vhost device features. The device features
+ * are accessed using BAR mapped registers.
+ */
+static u64 virtio_pci_epf_get_features(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+	u64 features;
+
+	vp_dev = to_vp_device(vdev);
+	ioaddr = vp_dev->ioaddr;
+
+	features = readl(ioaddr + HOST_FEATURES_UPPER);
+	features <<= 32;
+	features |= readl(ioaddr + HOST_FEATURES_LOWER);
+
+	return features;
+}
+
+/* virtio_pci_epf_finalize_features - virtio_config_ops to finalize features
+ *   with remote EPF vhost device
+ * @vdev: Virtio device that communicates with the remote vhost device
+ *
+ * Indicate the negotiated features to the remote EPF vhost device by sending
+ * HOST_CMD_FINALIZE_FEATURES command.
+ */
+static int virtio_pci_epf_finalize_features(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+	struct device *dev;
+	int ret;
+
+	vp_dev = to_vp_device(vdev);
+	dev = &vp_dev->pci_dev->dev;
+	ioaddr = vp_dev->ioaddr;
+
+	/* Give virtio_ring a chance to accept features. */
+	vring_transport_features(vdev);
+
+	writel(lower_32_bits(vdev->features), ioaddr + GUEST_FEATURES_LOWER);
+	writel(upper_32_bits(vdev->features), ioaddr + GUEST_FEATURES_UPPER);
+
+	ret = virtio_pci_epf_send_command(vp_dev, HOST_CMD_FINALIZE_FEATURES);
+	if (ret) {
+		dev_err(dev, "Failed to set configuration event vector\n");
+		return VIRTIO_MSI_NO_VECTOR;
+	}
+
+	return 0;
+}
+
+/* virtio_pci_epf_get - Copy the device configuration space data from
+ *   EPF device to buffer provided by virtio driver
+ * @vdev: Virtio device that communicates with the remote vhost device
+ * @offset: Offset in the device configuration space
+ * @buf: Buffer address from virtio driver where configuration space
+ *   data has to be copied
+ * @len: Length of the data from device configuration space to be copied
+ *
+ * Copy the device configuration space data to buffer provided by virtio
+ * driver.
+ */
+static void virtio_pci_epf_get(struct virtio_device *vdev, unsigned int offset,
+			       void *buf, unsigned int len)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+
+	vp_dev = to_vp_device(vdev);
+	ioaddr = vp_dev->ioaddr;
+
+	memcpy_fromio(buf, ioaddr + DEVICE_CFG_SPACE + offset, len);
+}
+
+/* virtio_pci_epf_set - Copy the device configuration space data from buffer
+ *   provided by virtio driver to EPF device
+ * @vdev: Virtio device that communicates with the remote vhost device
+ * @offset: Offset in the device configuration space
+ * @buf: Buffer address provided by virtio driver which has the configuration
+ *   space data to be copied
+ * @len: Length of the data from device configuration space to be copied
+ *
+ * Copy the device configuration space data from buffer provided by virtio
+ * driver to the EPF device.
+ */
+static void virtio_pci_epf_set(struct virtio_device *vdev, unsigned int offset,
+			       const void *buf, unsigned int len)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+
+	vp_dev = to_vp_device(vdev);
+	ioaddr = vp_dev->ioaddr;
+
+	memcpy_toio(ioaddr + DEVICE_CFG_SPACE + offset, buf, len);
+}
+
+/* virtio_pci_epf_get_status - EPF virtio_config_ops to get device status
+ * @vdev: Virtio device that communicates with the remote vhost device
+ *
+ * EPF virtio_config_ops to get device status. The remote EPF vhost device
+ * populates the vhost device status in BAR mapped region.
+ */
+static u8 virtio_pci_epf_get_status(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+
+	vp_dev = to_vp_device(vdev);
+	ioaddr = vp_dev->ioaddr;
+
+	return readb(ioaddr + DEVICE_STATUS);
+}
+
+/* virtio_pci_epf_set_status - EPF virtio_config_ops to set device status
+ * @vdev: Virtio device that communicates with the remote vhost device
+ *
+ * EPF virtio_config_ops to set device status. This function updates the
+ * status in scratchpad register and sends a notification to the vhost
+ * device using HOST_CMD_SET_STATUS command.
+ */
+static void virtio_pci_epf_set_status(struct virtio_device *vdev, u8 status)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+	struct device *dev;
+	int ret;
+
+	vp_dev = to_vp_device(vdev);
+	dev = &vp_dev->pci_dev->dev;
+	ioaddr = vp_dev->ioaddr;
+
+	/* We should never be setting status to 0. */
+	if (WARN_ON(!status))
+		return;
+
+	writeb(status, ioaddr + DEVICE_STATUS);
+
+	ret = virtio_pci_epf_send_command(vp_dev, HOST_CMD_SET_STATUS);
+	if (ret)
+		dev_err(dev, "Failed to set device status\n");
+}
+
+/* virtio_pci_epf_reset - EPF virtio_config_ops to reset the device
+ * @vdev: Virtio device that communicates with the remote vhost device
+ *
+ * EPF virtio_config_ops to reset the device. This sends HOST_CMD_RESET
+ * command to reset the device.
+ */
+static void virtio_pci_epf_reset(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev;
+	void __iomem *ioaddr;
+	struct device *dev;
+	int ret;
+
+	vp_dev = to_vp_device(vdev);
+	dev = &vp_dev->pci_dev->dev;
+	ioaddr = vp_dev->ioaddr;
+
+	ret = virtio_pci_epf_send_command(vp_dev, HOST_CMD_RESET);
+	if (ret)
+		dev_err(dev, "Failed to reset device\n");
+}
+
+/* virtio_pci_epf_config_vector - virtio_pci_device ops to set config vector
+ * @vp_dev: Virtio PCI device managed by virtio_pci_common.c
+ *
+ * virtio_pci_device ops to set config vector. This writes the config MSI-X
+ * vector to the BAR mapped region.
+ */
+static u16 virtio_pci_epf_config_vector(struct virtio_pci_device *vp_dev,
+					u16 vector)
+{
+	void __iomem *ioaddr = vp_dev->ioaddr;
+
+	writew(vector, ioaddr + MSIX_CONFIG);
+
+	return readw(ioaddr + MSIX_CONFIG);
+}
+
+/* virtio_pci_epf_notify - Send notification to the remote vhost virtqueue
+ * @vq: The local virtio virtqueue corresponding to the remote vhost virtqueue
+ *   where the notification has to be sent
+ *
+ * Send notification to the remote vhost virtqueue by using QUEUE_CMD_NOTIFY
+ * command.
+ */
+static bool virtio_pci_epf_notify(struct virtqueue *vq)
+{
+	struct virtio_pci_device *vp_dev;
+	struct device *dev;
+	int ret;
+
+	vp_dev = vq->priv;
+	dev = &vp_dev->pci_dev->dev;
+
+	ret = virtio_pci_epf_send_queue_command(vp_dev, vq, QUEUE_CMD_NOTIFY);
+	if (ret) {
+		dev_err(dev, "Notifying virtqueue: %d Failed\n", vq->index);
+		return false;
+	}
+
+	return true;
+}
+
+/* virtio_pci_epf_setup_vq - Configure virtqueue
+ * @vp_dev: Virtio PCI device managed by virtio_pci_common.c
+ * @info: Wrapper to virtqueue to maintain list of all queues
+ * @callback: Callback function that has to be associated with virtqueue
+ * @vq: The local virtio virtqueue corresponding to the remote vhost virtqueue
+ *   where the notification has to be sent
+ *
+ * Configure virtqueue with the number of buffers provided by EPF vhost device
+ * and associate a callback function for each of these virtqueues.
+ */
+static struct virtqueue *
+virtio_pci_epf_setup_vq(struct virtio_pci_device *vp_dev,
+			struct virtio_pci_vq_info *info, unsigned int index,
+			void (*callback)(struct virtqueue *vq),
+			const char *name, bool ctx, u16 msix_vec)
+{
+	u16 queue_num_buffers;
+	void __iomem *ioaddr;
+	struct virtqueue *vq;
+	struct device *dev;
+	dma_addr_t vq_addr;
+	u16 status;
+	int err;
+
+	dev = &vp_dev->pci_dev->dev;
+	ioaddr = vp_dev->ioaddr;
+
+	status = readw(ioaddr + QUEUE_STATUS(index));
+	if (status & STATUS_ACTIVE) {
+		dev_err(dev, "Virtqueue %d is already active\n", index);
+		return ERR_PTR(-ENOENT);
+	}
+
+	queue_num_buffers = readw(ioaddr + QUEUE_NUM_BUFFERS(index));
+	if (!queue_num_buffers) {
+		dev_err(dev, "Virtqueue %d is not available\n", index);
+		return ERR_PTR(-ENOENT);
+	}
+
+	info->msix_vector = msix_vec;
+
+	vq = vring_create_virtqueue(index, queue_num_buffers,
+				    VIRTIO_PCI_VRING_ALIGN, &vp_dev->vdev, true,
+				    false, ctx, virtio_pci_epf_notify, callback,
+				    name);
+	if (!vq) {
+		dev_err(dev, "Failed to create Virtqueue %d\n", index);
+		return ERR_PTR(-ENOMEM);
+	}
+	mutex_init(&vq->lock);
+
+	vq_addr = virtqueue_get_desc_addr(vq);
+	writel(lower_32_bits(vq_addr), ioaddr + QUEUE_ADDR_LOWER(index));
+	writel(upper_32_bits(vq_addr), ioaddr + QUEUE_ADDR_UPPER(index));
+
+	vq->priv = vp_dev;
+	writew(QUEUE_CMD_ACTIVATE, ioaddr + QUEUE_CMD(index));
+
+	err = virtio_pci_epf_send_queue_command(vp_dev, vq, QUEUE_CMD_ACTIVATE);
+	if (err) {
+		dev_err(dev, "Failed to activate Virtqueue %d\n", index);
+		goto out_del_vq;
+	}
+
+	if (msix_vec != VIRTIO_MSI_NO_VECTOR)
+		writew(msix_vec, ioaddr + QUEUE_MSIX_VECTOR(index));
+
+	return vq;
+
+out_del_vq:
+	vring_del_virtqueue(vq);
+
+	return ERR_PTR(err);
+}
+
+/* virtio_pci_epf_del_vq - Free memory allocated for virtio virtqueues
+ * @info: Wrapper to virtqueue to maintain list of all queues
+ *
+ * Free memory allocated for a virtqueue represented by @info
+ */
+static void virtio_pci_epf_del_vq(struct virtio_pci_vq_info *info)
+{
+	struct virtio_pci_device *vp_dev;
+	struct virtqueue *vq;
+	void __iomem *ioaddr;
+	unsigned int index;
+
+	vq = info->vq;
+	vp_dev = to_vp_device(vq->vdev);
+	ioaddr = vp_dev->ioaddr;
+	index = vq->index;
+
+	if (vp_dev->msix_enabled)
+		writew(VIRTIO_MSI_NO_VECTOR, ioaddr + QUEUE_MSIX_VECTOR(index));
+
+	writew(QUEUE_CMD_DEACTIVATE, ioaddr + QUEUE_CMD(index));
+	vring_del_virtqueue(vq);
+}
+
+static const struct virtio_config_ops virtio_pci_epf_config_ops = {
+	.get		= virtio_pci_epf_get,
+	.set		= virtio_pci_epf_set,
+	.get_status	= virtio_pci_epf_get_status,
+	.set_status	= virtio_pci_epf_set_status,
+	.reset		= virtio_pci_epf_reset,
+	.find_vqs	= vp_find_vqs,
+	.del_vqs	= vp_del_vqs,
+	.get_features	= virtio_pci_epf_get_features,
+	.finalize_features = virtio_pci_epf_finalize_features,
+	.bus_name	= vp_bus_name,
+	.set_vq_affinity = vp_set_vq_affinity,
+	.get_vq_affinity = vp_get_vq_affinity,
+};
+
+/* virtio_pci_epf_release_dev - Callback function to free device
+ * @dev: Device in virtio_device that has to be freed
+ *
+ * Callback function from device core invoked to free the device after
+ * all references have been removed. This frees the allocated memory for
+ * struct virtio_pci_epf.
+ */
+static void virtio_pci_epf_release_dev(struct device *dev)
+{
+	struct virtio_pci_device *vp_dev;
+	struct virtio_pci_epf *pci_epf;
+	struct virtio_device *vdev;
+
+	vdev = dev_to_virtio(dev);
+	vp_dev = to_vp_device(vdev);
+	pci_epf = to_virtio_pci_epf(vp_dev);
+
+	kfree(pci_epf);
+}
+
+/* virtio_pci_epf_probe - Initialize struct virtio_pci_epf when a new PCIe
+ *   device is created
+ * @pdev: The pci_dev that is created by the PCIe core during enumeration
+ * @id: pci_device_id of the @pdev
+ *
+ * Probe function to initialize struct virtio_pci_epf when a new PCIe device is
+ * created.
+ */
+static int virtio_pci_epf_probe(struct pci_dev *pdev,
+				const struct pci_device_id *id)
+{
+	struct virtio_pci_device *vp_dev, *reg_dev = NULL;
+	struct virtio_pci_epf *pci_epf;
+	struct device *dev;
+	int err;
+
+	if (pci_is_bridge(pdev))
+		return -ENODEV;
+
+	pci_epf = kzalloc(sizeof(*pci_epf), GFP_KERNEL);
+	if (!pci_epf)
+		return -ENOMEM;
+
+	dev = &pdev->dev;
+	vp_dev = &pci_epf->vp_dev;
+	vp_dev->vdev.dev.parent = dev;
+	vp_dev->vdev.dev.release = virtio_pci_epf_release_dev;
+	vp_dev->pci_dev = pdev;
+	INIT_LIST_HEAD(&vp_dev->virtqueues);
+	spin_lock_init(&vp_dev->lock);
+	mutex_init(&pci_epf->lock);
+
+	err = pci_enable_device(pdev);
+	if (err) {
+		dev_err(dev, "Cannot enable PCI device\n");
+		goto err_enable_device;
+	}
+
+	err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
+	if (err) {
+		dev_err(dev, "Cannot set DMA mask\n");
+		goto err_dma_set_mask;
+	}
+
+	err = pci_request_regions(pdev, DRV_MODULE_NAME);
+	if (err) {
+		dev_err(dev, "Cannot obtain PCI resources\n");
+		goto err_dma_set_mask;
+	}
+
+	pci_set_master(pdev);
+
+	vp_dev->ioaddr = pci_ioremap_bar(pdev, 0);
+	if (!vp_dev->ioaddr) {
+		dev_err(dev, "Failed to read BAR0\n");
+		goto err_ioremap;
+	}
+
+	pci_set_drvdata(pdev, vp_dev);
+	vp_dev->isr = vp_dev->ioaddr + ISR;
+
+	/*
+	 * we use the subsystem vendor/device id as the virtio vendor/device
+	 * id.  this allows us to use the same PCI vendor/device id for all
+	 * virtio devices and to identify the particular virtio driver by
+	 * the subsystem ids
+	 */
+	vp_dev->vdev.id.vendor = pdev->subsystem_vendor;
+	vp_dev->vdev.id.device = pdev->subsystem_device;
+
+	vp_dev->vdev.config = &virtio_pci_epf_config_ops;
+
+	vp_dev->config_vector = virtio_pci_epf_config_vector;
+	vp_dev->setup_vq = virtio_pci_epf_setup_vq;
+	vp_dev->del_vq = virtio_pci_epf_del_vq;
+
+	err = register_virtio_device(&vp_dev->vdev);
+	reg_dev = vp_dev;
+	if (err) {
+		dev_err(dev, "Failed to register VIRTIO device\n");
+		goto err_register_virtio;
+	}
+
+	return 0;
+
+err_register_virtio:
+	pci_iounmap(pdev, vp_dev->ioaddr);
+
+err_ioremap:
+	pci_release_regions(pdev);
+
+err_dma_set_mask:
+	pci_disable_device(pdev);
+
+err_enable_device:
+	if (reg_dev)
+		put_device(&vp_dev->vdev.dev);
+	else
+		kfree(vp_dev);
+
+	return err;
+}
+
+/* virtio_pci_epf_remove - Free the initializations performed by virtio_pci_epf_probe()
+ * @pdev: The pci_dev that is created by the PCIe core during enumeration
+ *
+ * Free the initializations performed by virtio_pci_epf_probe().
+ */
+void virtio_pci_epf_remove(struct pci_dev *pdev)
+{
+	struct virtio_pci_device *vp_dev;
+
+	vp_dev = pci_get_drvdata(pdev);
+
+	unregister_virtio_device(&vp_dev->vdev);
+	pci_iounmap(pdev, vp_dev->ioaddr);
+	pci_release_regions(pdev);
+	pci_disable_device(pdev);
+}
+
+static const struct pci_device_id virtio_pci_epf_table[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCI_DEVICE_ID_TI_DRA74x),
+	},
+	{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCI_DEVICE_ID_TI_DRA72x),
+	},
+	{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCI_DEVICE_ID_TI_J721E),
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(pci, virtio_pci_epf_table);
+
+static struct pci_driver virtio_pci_epf_driver = {
+	.name		= DRV_MODULE_NAME,
+	.id_table	= virtio_pci_epf_table,
+	.probe		= virtio_pci_epf_probe,
+	.remove		= virtio_pci_epf_remove,
+	.sriov_configure = pci_sriov_configure_simple,
+};
+module_pci_driver(virtio_pci_epf_driver);
+
+MODULE_DESCRIPTION("VIRTIO PCI EPF DRIVER");
+MODULE_AUTHOR("Kishon Vijay Abraham I <kishon@ti.com>");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index a493eac08393..0eb51b31545d 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -19,6 +19,7 @@
  * @priv: a pointer for the virtqueue implementation to use.
  * @index: the zero-based ordinal number for this queue.
  * @num_free: number of elements we expect to be able to fit.
+ * @mutex: mutex to protect concurrent access to the same queue
  *
  * A note on @num_free: with indirect buffers, each buffer needs one
  * element in the queue, otherwise a buffer will need one element per
@@ -31,6 +32,8 @@ struct virtqueue {
 	struct virtio_device *vdev;
 	unsigned int index;
 	unsigned int num_free;
+	/* mutex to protect concurrent access to the queue while configuring */
+	struct mutex lock;
 	void *priv;
 };
 
-- 
2.17.1