Introduce a vfio driver over virtio devices to support the legacy
interface functionality for VFs.

Background, from the virtio spec [1].
--------------------------------------------------------------------
In some systems, there is a need to support a virtio legacy driver with
a device that does not directly support the legacy interface. In such
scenarios, a group owner device can provide the legacy interface
functionality for the group member devices. The driver of the owner
device can then access the legacy interface of a member device on behalf
of the legacy member device driver.

For example, with the SR-IOV group type, group members (VFs) can not
present the legacy interface in an I/O BAR in BAR0 as expected by the
legacy pci driver. If the legacy driver is running inside a virtual
machine, the hypervisor executing the virtual machine can present a
virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
legacy driver accesses to this I/O BAR and forwards them to the group
owner device (PF) using group administration commands.
--------------------------------------------------------------------

Specifically, this driver adds support for a virtio-net VF to be exposed
as a transitional device to a guest driver and allows the legacy IO BAR
functionality on top.

This allows a VM which uses a legacy virtio-net driver in the guest to
work transparently over a VF which its driver in the host is that new
driver.

The driver can be extended easily to support some other types of virtio
devices (e.g virtio-blk), by adding in a few places the specific type
properties as was done for virtio-net.

For now, only the virtio-net use case was tested and as such we introduce
the support only for such a device.

Practically,
Upon probing a VF for a virtio-net device, in case its PF supports
legacy access over the virtio admin commands and the VF doesn't have BAR
0, we set some specific 'vfio_device_ops' to be able to simulate in SW a
transitional device with I/O BAR in BAR 0.

The existence of the simulated I/O bar is reported later on by
overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
exposes itself as a transitional device by overwriting some properties
upon reading its config space.

Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
guest may use it via read/write calls according to the virtio
specification.

Any read/write towards the control parts of the BAR will be captured by
the new driver and will be translated into admin commands towards the
device.

Any data path read/write access (i.e. virtio driver notifications) will
be forwarded to the physical BAR which its properties were supplied by
the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.

With that code in place a legacy driver in the guest has the look and
feel as if having a transitional device with legacy support for both its
control and data path flows.

[1]
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c

Signed-off-by: Yishai Hadas <yish...@nvidia.com>
---
 MAINTAINERS                      |   6 +
 drivers/vfio/pci/Kconfig         |   2 +
 drivers/vfio/pci/Makefile        |   2 +
 drivers/vfio/pci/virtio/Kconfig  |  15 +
 drivers/vfio/pci/virtio/Makefile |   4 +
 drivers/vfio/pci/virtio/cmd.c    |   4 +-
 drivers/vfio/pci/virtio/cmd.h    |   8 +
 drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
 8 files changed, 585 insertions(+), 2 deletions(-)
 create mode 100644 drivers/vfio/pci/virtio/Kconfig
 create mode 100644 drivers/vfio/pci/virtio/Makefile
 create mode 100644 drivers/vfio/pci/virtio/main.c

diff --git a/MAINTAINERS b/MAINTAINERS
index bf0f54c24f81..5098418c8389 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22624,6 +22624,12 @@ L:     k...@vger.kernel.org
 S:     Maintained
 F:     drivers/vfio/pci/mlx5/
 
+VFIO VIRTIO PCI DRIVER
+M:     Yishai Hadas <yish...@nvidia.com>
+L:     k...@vger.kernel.org
+S:     Maintained
+F:     drivers/vfio/pci/virtio
+
 VFIO PCI DEVICE SPECIFIC DRIVERS
 R:     Jason Gunthorpe <j...@nvidia.com>
 R:     Yishai Hadas <yish...@nvidia.com>
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 8125e5f37832..18c397df566d 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
 
 source "drivers/vfio/pci/pds/Kconfig"
 
+source "drivers/vfio/pci/virtio/Kconfig"
+
 endmenu
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index 45167be462d8..046139a4eca5 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
 obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
 
 obj-$(CONFIG_PDS_VFIO_PCI) += pds/
+
+obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
diff --git a/drivers/vfio/pci/virtio/Kconfig b/drivers/vfio/pci/virtio/Kconfig
new file mode 100644
index 000000000000..89eddce8b1bd
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config VIRTIO_VFIO_PCI
+        tristate "VFIO support for VIRTIO PCI devices"
+        depends on VIRTIO_PCI
+        select VFIO_PCI_CORE
+        help
+          This provides support for exposing VIRTIO VF devices using the VFIO
+          framework that can work with a legacy virtio driver in the guest.
+          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs shall
+          not indicate I/O Space.
+          As of that this driver emulated I/O BAR in software to let a VF be
+          seen as a transitional device in the guest and let it work with
+          a legacy driver.
+
+          If you don't know what to do here, say N.
diff --git a/drivers/vfio/pci/virtio/Makefile b/drivers/vfio/pci/virtio/Makefile
new file mode 100644
index 000000000000..584372648a03
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
+virtio-vfio-pci-y := main.o cmd.o
+
diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
index f068239cdbb0..aea9d25fbf1d 100644
--- a/drivers/vfio/pci/virtio/cmd.c
+++ b/drivers/vfio/pci/virtio/cmd.c
@@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device 
*virtvdev, u16 opcode,
 {
        struct virtio_device *virtio_dev =
                virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
-       struct virtio_admin_cmd_data_lr_write *in;
+       struct virtio_admin_cmd_legacy_wr_data *in;
        struct scatterlist in_sg;
        struct virtio_admin_cmd cmd = {};
        int ret;
@@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device 
*virtvdev, u16 opcode,
 {
        struct virtio_device *virtio_dev =
                virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
-       struct virtio_admin_cmd_data_lr_read *in;
+       struct virtio_admin_cmd_legacy_rd_data *in;
        struct scatterlist in_sg, out_sg;
        struct virtio_admin_cmd cmd = {};
        int ret;
diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
index c2a3645f4b90..347b1dc85570 100644
--- a/drivers/vfio/pci/virtio/cmd.h
+++ b/drivers/vfio/pci/virtio/cmd.h
@@ -13,7 +13,15 @@
 
 struct virtiovf_pci_core_device {
        struct vfio_pci_core_device core_device;
+       u8 bar0_virtual_buf_size;
+       u8 *bar0_virtual_buf;
+       /* synchronize access to the virtual buf */
+       struct mutex bar_mutex;
        int vf_id;
+       void __iomem *notify_addr;
+       u32 notify_offset;
+       u8 notify_bar;
+       u8 pci_cmd_io :1;
 };
 
 int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
diff --git a/drivers/vfio/pci/virtio/main.c b/drivers/vfio/pci/virtio/main.c
new file mode 100644
index 000000000000..2486991c49f3
--- /dev/null
+++ b/drivers/vfio/pci/virtio/main.c
@@ -0,0 +1,546 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/pm_runtime.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/vfio.h>
+#include <linux/vfio_pci_core.h>
+#include <linux/virtio_pci.h>
+#include <linux/virtio_net.h>
+#include <linux/virtio_pci_modern.h>
+
+#include "cmd.h"
+
+#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
+#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
+
+static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device *virtvdev,
+                                loff_t pos, char __user *buf,
+                                size_t count, bool read)
+{
+       u8 *bar0_buf = virtvdev->bar0_virtual_buf;
+       u16 opcode;
+       int ret;
+
+       mutex_lock(&virtvdev->bar_mutex);
+       if (read) {
+               opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
+                       VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
+                       VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
+               ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
+                                          count, bar0_buf + pos);
+               if (ret)
+                       goto out;
+               if (copy_to_user(buf, bar0_buf + pos, count))
+                       ret = -EFAULT;
+               goto out;
+       }
+
+       if (copy_from_user(bar0_buf + pos, buf, count)) {
+               ret = -EFAULT;
+               goto out;
+       }
+
+       opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
+                       VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
+                       VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;
+       ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
+                                   bar0_buf + pos);
+out:
+       mutex_unlock(&virtvdev->bar_mutex);
+       return ret;
+}
+
+static int
+translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
+                           loff_t pos, char __user *buf,
+                           size_t count, bool read)
+{
+       struct vfio_pci_core_device *core_device = &virtvdev->core_device;
+       u16 queue_notify;
+       int ret;
+
+       if (pos + count > virtvdev->bar0_virtual_buf_size)
+               return -EINVAL;
+
+       switch (pos) {
+       case VIRTIO_PCI_QUEUE_NOTIFY:
+               if (count != sizeof(queue_notify))
+                       return -EINVAL;
+               if (read) {
+                       ret = vfio_pci_ioread16(core_device, true, 
&queue_notify,
+                                               virtvdev->notify_addr);
+                       if (ret)
+                               return ret;
+                       if (copy_to_user(buf, &queue_notify,
+                                        sizeof(queue_notify)))
+                               return -EFAULT;
+                       break;
+               }
+
+               if (copy_from_user(&queue_notify, buf, count))
+                       return -EFAULT;
+
+               ret = vfio_pci_iowrite16(core_device, true, queue_notify,
+                                        virtvdev->notify_addr);
+               break;
+       default:
+               ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
+       }
+
+       return ret ? ret : count;
+}
+
+static bool range_contains_range(loff_t range1_start, size_t count1,
+                                loff_t range2_start, size_t count2,
+                                loff_t *start_offset)
+{
+       if (range1_start <= range2_start &&
+           range1_start + count1 >= range2_start + count2) {
+               *start_offset = range2_start - range1_start;
+               return true;
+       }
+       return false;
+}
+
+static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
+                                       char __user *buf, size_t count,
+                                       loff_t *ppos)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+       loff_t copy_offset;
+       __le32 val32;
+       __le16 val16;
+       u8 val8;
+       int ret;
+
+       ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
+       if (ret < 0)
+               return ret;
+
+       if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
+                                &copy_offset)) {
+               val16 = cpu_to_le16(0x1000);
+               if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+                       return -EFAULT;
+       }
+
+       if (virtvdev->pci_cmd_io &&
+           range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
+                                &copy_offset)) {
+               if (copy_from_user(&val16, buf, sizeof(val16)))
+                       return -EFAULT;
+               val16 |= cpu_to_le16(PCI_COMMAND_IO);
+               if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+                       return -EFAULT;
+       }
+
+       if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
+                                &copy_offset)) {
+               /* Transional needs to have revision 0 */
+               val8 = 0;
+               if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
+                       return -EFAULT;
+       }
+
+       if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
+                                &copy_offset)) {
+               val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
+               if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
+                       return -EFAULT;
+       }
+
+       if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
+                                &copy_offset)) {
+               /* Transitional devices use the PCI subsystem device id as
+                * virtio device id, same as legacy driver always did.
+                */
+               val16 = cpu_to_le16(VIRTIO_ID_NET);
+               if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+                       return -EFAULT;
+       }
+
+       return count;
+}
+
+static ssize_t
+virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
+                      size_t count, loff_t *ppos)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       struct pci_dev *pdev = virtvdev->core_device.pdev;
+       unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+       loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+       int ret;
+
+       if (!count)
+               return 0;
+
+       if (index == VFIO_PCI_CONFIG_REGION_INDEX)
+               return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
+
+       if (index != VFIO_PCI_BAR0_REGION_INDEX)
+               return vfio_pci_core_read(core_vdev, buf, count, ppos);
+
+       ret = pm_runtime_resume_and_get(&pdev->dev);
+       if (ret) {
+               pci_info_ratelimited(pdev, "runtime resume failed %d\n",
+                                    ret);
+               return -EIO;
+       }
+
+       ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
+       pm_runtime_put(&pdev->dev);
+       return ret;
+}
+
+static ssize_t
+virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user *buf,
+                       size_t count, loff_t *ppos)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       struct pci_dev *pdev = virtvdev->core_device.pdev;
+       unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+       loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+       int ret;
+
+       if (!count)
+               return 0;
+
+       if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
+               loff_t copy_offset;
+               u16 cmd;
+
+               if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
+                                        &copy_offset)) {
+                       if (copy_from_user(&cmd, buf + copy_offset, 
sizeof(cmd)))
+                               return -EFAULT;
+                       virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
+               }
+       }
+
+       if (index != VFIO_PCI_BAR0_REGION_INDEX)
+               return vfio_pci_core_write(core_vdev, buf, count, ppos);
+
+       ret = pm_runtime_resume_and_get(&pdev->dev);
+       if (ret) {
+               pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
+               return -EIO;
+       }
+
+       ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf, 
count, false);
+       pm_runtime_put(&pdev->dev);
+       return ret;
+}
+
+static int
+virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
+                                  unsigned int cmd, unsigned long arg)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       unsigned long minsz = offsetofend(struct vfio_region_info, offset);
+       void __user *uarg = (void __user *)arg;
+       struct vfio_region_info info = {};
+
+       if (copy_from_user(&info, uarg, minsz))
+               return -EFAULT;
+
+       if (info.argsz < minsz)
+               return -EINVAL;
+
+       switch (info.index) {
+       case VFIO_PCI_BAR0_REGION_INDEX:
+               info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+               info.size = virtvdev->bar0_virtual_buf_size;
+               info.flags = VFIO_REGION_INFO_FLAG_READ |
+                            VFIO_REGION_INFO_FLAG_WRITE;
+               return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
+       default:
+               return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+       }
+}
+
+static long
+virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int cmd,
+                            unsigned long arg)
+{
+       switch (cmd) {
+       case VFIO_DEVICE_GET_REGION_INFO:
+               return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
+       default:
+               return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+       }
+}
+
+static int
+virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
+{
+       struct vfio_pci_core_device *core_device = &virtvdev->core_device;
+       int ret;
+
+       /* Setup the BAR where the 'notify' exists to be used by vfio as well
+        * This will let us mmap it only once and use it when needed.
+        */
+       ret = vfio_pci_core_setup_barmap(core_device,
+                                        virtvdev->notify_bar);
+       if (ret)
+               return ret;
+
+       virtvdev->notify_addr = core_device->barmap[virtvdev->notify_bar] +
+                       virtvdev->notify_offset;
+       return 0;
+}
+
+static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       struct vfio_pci_core_device *vdev = &virtvdev->core_device;
+       int ret;
+
+       ret = vfio_pci_core_enable(vdev);
+       if (ret)
+               return ret;
+
+       if (virtvdev->bar0_virtual_buf) {
+               /* upon close_device() the vfio_pci_core_disable() is called
+                * and will close all the previous mmaps, so it seems that the
+                * valid life cycle for the 'notify' addr is per open/close.
+                */
+               ret = virtiovf_set_notify_addr(virtvdev);
+               if (ret) {
+                       vfio_pci_core_disable(vdev);
+                       return ret;
+               }
+       }
+
+       vfio_pci_core_finish_enable(vdev);
+       return 0;
+}
+
+static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
+{
+       vfio_pci_core_close_device(core_vdev);
+}
+
+static int virtiovf_get_device_config_size(unsigned short device)
+{
+       switch (device) {
+       case 0x1041:
+               /* network card */
+               return offsetofend(struct virtio_net_config, status);
+       default:
+               return 0;
+       }
+}
+
+static int virtiovf_read_notify_info(struct virtiovf_pci_core_device *virtvdev)
+{
+       u64 offset;
+       int ret;
+       u8 bar;
+
+       ret = virtiovf_cmd_lq_read_notify(virtvdev,
+                               VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
+                               &bar, &offset);
+       if (ret)
+               return ret;
+
+       virtvdev->notify_bar = bar;
+       virtvdev->notify_offset = offset;
+       return 0;
+}
+
+static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+       struct pci_dev *pdev;
+       int ret;
+
+       ret = vfio_pci_core_init_dev(core_vdev);
+       if (ret)
+               return ret;
+
+       pdev = virtvdev->core_device.pdev;
+       virtvdev->vf_id = pci_iov_vf_id(pdev);
+       if (virtvdev->vf_id < 0)
+               return -EINVAL;
+
+       ret = virtiovf_read_notify_info(virtvdev);
+       if (ret)
+               return ret;
+
+       virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
+               VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
+               virtiovf_get_device_config_size(pdev->device);
+       virtvdev->bar0_virtual_buf = kzalloc(virtvdev->bar0_virtual_buf_size,
+                                            GFP_KERNEL);
+       if (!virtvdev->bar0_virtual_buf)
+               return -ENOMEM;
+       mutex_init(&virtvdev->bar_mutex);
+       return 0;
+}
+
+static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
+{
+       struct virtiovf_pci_core_device *virtvdev = container_of(
+               core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+
+       kfree(virtvdev->bar0_virtual_buf);
+       vfio_pci_core_release_dev(core_vdev);
+}
+
+static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
+       .name = "virtio-transitional-vfio-pci",
+       .init = virtiovf_pci_init_device,
+       .release = virtiovf_pci_core_release_dev,
+       .open_device = virtiovf_pci_open_device,
+       .close_device = virtiovf_pci_close_device,
+       .ioctl = virtiovf_vfio_pci_core_ioctl,
+       .read = virtiovf_pci_core_read,
+       .write = virtiovf_pci_core_write,
+       .mmap = vfio_pci_core_mmap,
+       .request = vfio_pci_core_request,
+       .match = vfio_pci_core_match,
+       .bind_iommufd = vfio_iommufd_physical_bind,
+       .unbind_iommufd = vfio_iommufd_physical_unbind,
+       .attach_ioas = vfio_iommufd_physical_attach_ioas,
+};
+
+static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
+       .name = "virtio-acc-vfio-pci",
+       .init = vfio_pci_core_init_dev,
+       .release = vfio_pci_core_release_dev,
+       .open_device = virtiovf_pci_open_device,
+       .close_device = virtiovf_pci_close_device,
+       .ioctl = vfio_pci_core_ioctl,
+       .device_feature = vfio_pci_core_ioctl_feature,
+       .read = vfio_pci_core_read,
+       .write = vfio_pci_core_write,
+       .mmap = vfio_pci_core_mmap,
+       .request = vfio_pci_core_request,
+       .match = vfio_pci_core_match,
+       .bind_iommufd = vfio_iommufd_physical_bind,
+       .unbind_iommufd = vfio_iommufd_physical_unbind,
+       .attach_ioas = vfio_iommufd_physical_attach_ioas,
+};
+
+static bool virtiovf_bar0_exists(struct pci_dev *pdev)
+{
+       struct resource *res = pdev->resource;
+
+       return res->flags ? true : false;
+}
+
+#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
+       (BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
+        BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
+
+static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
+{
+       int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
+       u8 *buf;
+       int ret;
+
+       /* Only virtio-net is supported/tested so far */
+       if (pdev->device != 0x1041)
+               return false;
+
+       buf = kzalloc(buf_size, GFP_KERNEL);
+       if (!buf)
+               return false;
+
+       ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
+       if (ret)
+               goto end;
+
+       if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP) !=
+               VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
+               ret = -EOPNOTSUPP;
+               goto end;
+       }
+
+       /* confirm the used commands */
+       memset(buf, 0, buf_size);
+       *(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
+       ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
+
+end:
+       kfree(buf);
+       return ret ? false : true;
+}
+
+static int virtiovf_pci_probe(struct pci_dev *pdev,
+                             const struct pci_device_id *id)
+{
+       const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
+       struct virtiovf_pci_core_device *virtvdev;
+       int ret;
+
+       if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev) &&
+           !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
+               ops = &virtiovf_acc_vfio_pci_tran_ops;
+
+       virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
+                                    &pdev->dev, ops);
+       if (IS_ERR(virtvdev))
+               return PTR_ERR(virtvdev);
+
+       dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
+       ret = vfio_pci_core_register_device(&virtvdev->core_device);
+       if (ret)
+               goto out;
+       return 0;
+out:
+       vfio_put_device(&virtvdev->core_device.vdev);
+       return ret;
+}
+
+static void virtiovf_pci_remove(struct pci_dev *pdev)
+{
+       struct virtiovf_pci_core_device *virtvdev = dev_get_drvdata(&pdev->dev);
+
+       vfio_pci_core_unregister_device(&virtvdev->core_device);
+       vfio_put_device(&virtvdev->core_device.vdev);
+}
+
+static const struct pci_device_id virtiovf_pci_table[] = {
+       { PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET, 
PCI_ANY_ID) },
+       {}
+};
+
+MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
+
+static struct pci_driver virtiovf_pci_driver = {
+       .name = KBUILD_MODNAME,
+       .id_table = virtiovf_pci_table,
+       .probe = virtiovf_pci_probe,
+       .remove = virtiovf_pci_remove,
+       .err_handler = &vfio_pci_core_err_handlers,
+       .driver_managed_dma = true,
+};
+
+module_pci_driver(virtiovf_pci_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Yishai Hadas <yish...@nvidia.com>");
+MODULE_DESCRIPTION(
+       "VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device family");
-- 
2.27.0

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