[V2,vfio,9/9] vfio/virtio: Introduce a vfio driver over virtio devices

Commit Message

Yishai Hadas Oct. 29, 2023, 3:59 p.m. UTC

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 admin command VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO 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 <[e-mail]>
---
 MAINTAINERS                      |   7 +
 drivers/vfio/pci/Kconfig         |   2 +
 drivers/vfio/pci/Makefile        |   2 +
 drivers/vfio/pci/virtio/Kconfig  |  16 +
 drivers/vfio/pci/virtio/Makefile |   4 +
 drivers/vfio/pci/virtio/main.c   | 551 +++++++++++++++++++++++++++++++
 6 files changed, 582 insertions(+)
 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

Comments

Yi Liu Oct. 31, 2023, 8:17 a.m. UTC | #1

On 2023/10/29 23:59, Yishai Hadas wrote:
> 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.
> --------------------------------------------------------------------

a dumb question. Is it common between all virtio devices that the legay
interface is in BAR0?

> 
> 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 admin command VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO 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 <[e-mail]>
> ---
>   MAINTAINERS                      |   7 +
>   drivers/vfio/pci/Kconfig         |   2 +
>   drivers/vfio/pci/Makefile        |   2 +
>   drivers/vfio/pci/virtio/Kconfig  |  16 +
>   drivers/vfio/pci/virtio/Makefile |   4 +
>   drivers/vfio/pci/virtio/main.c   | 551 +++++++++++++++++++++++++++++++
>   6 files changed, 582 insertions(+)
>   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 dd5de540ec0b..f59f84a6992d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22622,6 +22622,13 @@ L:	[e-mail]
>   S:	Maintained
>   F:	drivers/vfio/pci/mlx5/
>   
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <[e-mail]>
> +L:	[e-mail]
> +L:	[e-mail]
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>   VFIO PCI DEVICE SPECIFIC DRIVERS
>   R:	Jason Gunthorpe <[e-mail]>
>   R:	Yishai Hadas <[e-mail]>
> 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..3a6707639220
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Kconfig
> @@ -0,0 +1,16 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VIRTIO_VFIO_PCI
> +        tristate "VFIO support for VIRTIO NET PCI devices"
> +        depends on VIRTIO_PCI
> +        select VFIO_PCI_CORE
> +        help
> +          This provides support for exposing VIRTIO NET VF devices which support
> +          legacy IO access, 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..2039b39fb723
> --- /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
> +
> diff --git a/drivers/vfio/pci/virtio/main.c b/drivers/vfio/pci/virtio/main.c
> new file mode 100644
> index 000000000000..0f7d2f442f6c
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/main.c
> @@ -0,0 +1,551 @@
> +// 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_admin.h>
> +
> +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;
> +	void __iomem *notify_addr;
> +	u64 notify_offset;
> +	__le32 pci_base_addr_0;
> +	__le16 pci_cmd;
> +	u8 notify_bar;
> +};
> +
> +static int
> +virtiovf_issue_legacy_rw_cmd(struct virtiovf_pci_core_device *virtvdev,
> +			     loff_t pos, char __user *buf,
> +			     size_t count, bool read)
> +{
> +	bool msix_enabled =
> +		(virtvdev->core_device.irq_type == VFIO_PCI_MSIX_IRQ_INDEX);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
> +	bool common;
> +	int ret;
> +
> +	common = pos < VIRTIO_PCI_CONFIG_OFF(msix_enabled);
> +	mutex_lock(&virtvdev->bar_mutex);
> +	if (read) {
> +		if (common)
> +			ret = virtio_pci_admin_legacy_common_io_read(pdev, pos,
> +					count, bar0_buf + pos);
> +		else
> +			ret = virtio_pci_admin_legacy_device_io_read(pdev, pos,
> +					count, bar0_buf + pos);
> +		if (ret)
> +			goto out;
> +		if (copy_to_user(buf, bar0_buf + pos, count))
> +			ret = -EFAULT;
> +	} else {
> +		if (copy_from_user(bar0_buf + pos, buf, count)) {
> +			ret = -EFAULT;
> +			goto out;
> +		}
> +
> +		if (common)
> +			ret = virtio_pci_admin_legacy_common_io_write(pdev, pos,
> +					count, bar0_buf + pos);
> +		else
> +			ret = virtio_pci_admin_legacy_device_io_write(pdev, 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;
> +		} else {
> +			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_legacy_rw_cmd(virtvdev, pos, buf, count,
> +						   read);
> +	}
> +
> +	return ret ? ret : count;
> +}
> +
> +static bool range_intersect_range(loff_t range1_start, size_t count1,
> +				  loff_t range2_start, size_t count2,
> +				  loff_t *start_offset,
> +				  size_t *intersect_count,
> +				  size_t *register_offset)
> +{
> +	if (range1_start <= range2_start &&
> +	    range1_start + count1 > range2_start) {
> +		*start_offset = range2_start - range1_start;
> +		*intersect_count = min_t(size_t, count2,
> +					 range1_start + count1 - range2_start);
> +		*register_offset = 0;
> +		return true;
> +	}
> +
> +	if (range1_start > range2_start &&
> +	    range1_start < range2_start + count2) {
> +		*start_offset = 0;
> +		*intersect_count = min_t(size_t, count1,
> +					 range2_start + count2 - range1_start);
> +		*register_offset = range1_start - range2_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;
> +	size_t register_offset;
> +	loff_t copy_offset;
> +	size_t copy_count;
> +	__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_intersect_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
> +				  &copy_offset, &copy_count, &register_offset)) {
> +		val16 = cpu_to_le16(VIRTIO_TRANS_ID_NET);
> +		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset, copy_count))
> +			return -EFAULT;
> +	}
> +
> +	if ((le16_to_cpu(virtvdev->pci_cmd) & PCI_COMMAND_IO) &&
> +	    range_intersect_range(pos, count, PCI_COMMAND, sizeof(val16),
> +				  &copy_offset, &copy_count, &register_offset)) {
> +		if (copy_from_user((void *)&val16 + register_offset, buf + copy_offset,
> +				   copy_count))
> +			return -EFAULT;
> +		val16 |= cpu_to_le16(PCI_COMMAND_IO);
> +		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset,
> +				 copy_count))
> +			return -EFAULT;
> +	}
> +
> +	if (range_intersect_range(pos, count, PCI_REVISION_ID, sizeof(val8),
> +				  &copy_offset, &copy_count, &register_offset)) {
> +		/* Transional needs to have revision 0 */
> +		val8 = 0;
> +		if (copy_to_user(buf + copy_offset, &val8, copy_count))
> +			return -EFAULT;
> +	}
> +
> +	if (range_intersect_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
> +				  &copy_offset, &copy_count, &register_offset)) {
> +		u8 log_bar_size = ilog2(roundup_pow_of_two(virtvdev->bar0_virtual_buf_size));
> +		u32 mask_size = ~((BIT(log_bar_size) - 1));
> +		u32 pci_base_addr_0 = le32_to_cpu(virtvdev->pci_base_addr_0);
> +
> +		val32 = cpu_to_le32((pci_base_addr_0 & mask_size) | PCI_BASE_ADDRESS_SPACE_IO);
> +		if (copy_to_user(buf + copy_offset, (void *)&val32 + register_offset, copy_count))
> +			return -EFAULT;
> +	}
> +
> +	if (range_intersect_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
> +				  &copy_offset, &copy_count, &register_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, (void *)&val16 + register_offset,
> +				 copy_count))
> +			return -EFAULT;
> +	}
> +
> +	if (range_intersect_range(pos, count, PCI_SUBSYSTEM_VENDOR_ID, sizeof(val16),
> +				  &copy_offset, &copy_count, &register_offset)) {
> +		val16 = cpu_to_le16(PCI_VENDOR_ID_REDHAT_QUMRANET);
> +		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset,
> +				 copy_count))
> +			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) {
> +		size_t register_offset;
> +		loff_t copy_offset;
> +		size_t copy_count;
> +
> +		if (range_intersect_range(pos, count, PCI_COMMAND, sizeof(virtvdev->pci_cmd),
> +					  &copy_offset, &copy_count,
> +					  &register_offset)) {
> +			if (copy_from_user((void *)&virtvdev->pci_cmd + register_offset,
> +					   buf + copy_offset,
> +					   copy_count))
> +				return -EFAULT;
> +		}
> +
> +		if (range_intersect_range(pos, count, PCI_BASE_ADDRESS_0,
> +					  sizeof(virtvdev->pci_base_addr_0),
> +					  &copy_offset, &copy_count,
> +					  &register_offset)) {
> +			if (copy_from_user((void *)&virtvdev->pci_base_addr_0 + register_offset,
> +					   buf + copy_offset,
> +					   copy_count))
> +				return -EFAULT;
> +		}
> +	}
> +
> +	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 int virtiovf_get_device_config_size(unsigned short device)
> +{
> +	/* Network card */
> +	return offsetofend(struct virtio_net_config, status);
> +}
> +
> +static int virtiovf_read_notify_info(struct virtiovf_pci_core_device *virtvdev)
> +{
> +	u64 offset;
> +	int ret;
> +	u8 bar;
> +
> +	ret = virtio_pci_admin_legacy_io_notify_info(virtvdev->core_device.pdev,
> +				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;
> +	ret = virtiovf_read_notify_info(virtvdev);
> +	if (ret)
> +		return ret;
> +
> +	/* Being ready with a buffer that supports MSIX */
> +	virtvdev->bar0_virtual_buf_size = VIRTIO_PCI_CONFIG_OFF(true) +
> +				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-vfio-pci-trans",
> +	.init = virtiovf_pci_init_device,
> +	.release = virtiovf_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = vfio_pci_core_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_vfio_pci_ops = {
> +	.name = "virtio-vfio-pci",
> +	.init = vfio_pci_core_init_dev,
> +	.release = vfio_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = vfio_pci_core_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;
> +}
> +
> +static int virtiovf_pci_probe(struct pci_dev *pdev,
> +			      const struct pci_device_id *id)
> +{
> +	const struct vfio_device_ops *ops = &virtiovf_vfio_pci_ops;
> +	struct virtiovf_pci_core_device *virtvdev;
> +	int ret;
> +
> +	if (pdev->is_virtfn && virtio_pci_admin_has_legacy_io(pdev) &&
> +	    !virtiovf_bar0_exists(pdev))

nit. virtio_pci_admin_has_legacy_io() gives an impression that it is
checking the input pdev. However, it is checking its PF. may be worth
to make it more clearer.

> +		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[] = {
> +	/* Only virtio-net is supported/tested so far */
> +	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1041) },
> +	{}
> +};
> +
> +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 <[e-mail]>");
> +MODULE_DESCRIPTION(
> +	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO NET devices");

Michael S. Tsirkin Oct. 31, 2023, 8:23 a.m. UTC | #2

On Tue, Oct 31, 2023 at 04:17:45PM +0800, Yi Liu wrote:
> a dumb question. Is it common between all virtio devices that the legay
> interface is in BAR0?

It has to be, that is where the legacy driver is looking for it.

Yi Liu Oct. 31, 2023, 8:34 a.m. UTC | #3

On 2023/10/31 16:23, Michael S. Tsirkin wrote:
> On Tue, Oct 31, 2023 at 04:17:45PM +0800, Yi Liu wrote:
>> a dumb question. Is it common between all virtio devices that the legay
>> interface is in BAR0?
> 
> It has to be, that is where the legacy driver is looking for it.

sure. this makes sense.

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index dd5de540ec0b..f59f84a6992d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22622,6 +22622,13 @@  L:	[e-mail]
 S:	Maintained
 F:	drivers/vfio/pci/mlx5/
 
+VFIO VIRTIO PCI DRIVER
+M:	Yishai Hadas <[e-mail]>
+L:	[e-mail]
+L:	[e-mail]
+S:	Maintained
+F:	drivers/vfio/pci/virtio
+
 VFIO PCI DEVICE SPECIFIC DRIVERS
 R:	Jason Gunthorpe <[e-mail]>
 R:	Yishai Hadas <[e-mail]>
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..3a6707639220
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Kconfig
@@ -0,0 +1,16 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+config VIRTIO_VFIO_PCI
+        tristate "VFIO support for VIRTIO NET PCI devices"
+        depends on VIRTIO_PCI
+        select VFIO_PCI_CORE
+        help
+          This provides support for exposing VIRTIO NET VF devices which support
+          legacy IO access, 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..2039b39fb723
--- /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
+
diff --git a/drivers/vfio/pci/virtio/main.c b/drivers/vfio/pci/virtio/main.c
new file mode 100644
index 000000000000..0f7d2f442f6c
--- /dev/null
+++ b/drivers/vfio/pci/virtio/main.c
@@ -0,0 +1,551 @@ 
+// 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_admin.h>
+
+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;
+	void __iomem *notify_addr;
+	u64 notify_offset;
+	__le32 pci_base_addr_0;
+	__le16 pci_cmd;
+	u8 notify_bar;
+};
+
+static int
+virtiovf_issue_legacy_rw_cmd(struct virtiovf_pci_core_device *virtvdev,
+			     loff_t pos, char __user *buf,
+			     size_t count, bool read)
+{
+	bool msix_enabled =
+		(virtvdev->core_device.irq_type == VFIO_PCI_MSIX_IRQ_INDEX);
+	struct pci_dev *pdev = virtvdev->core_device.pdev;
+	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
+	bool common;
+	int ret;
+
+	common = pos < VIRTIO_PCI_CONFIG_OFF(msix_enabled);
+	mutex_lock(&virtvdev->bar_mutex);
+	if (read) {
+		if (common)
+			ret = virtio_pci_admin_legacy_common_io_read(pdev, pos,
+					count, bar0_buf + pos);
+		else
+			ret = virtio_pci_admin_legacy_device_io_read(pdev, pos,
+					count, bar0_buf + pos);
+		if (ret)
+			goto out;
+		if (copy_to_user(buf, bar0_buf + pos, count))
+			ret = -EFAULT;
+	} else {
+		if (copy_from_user(bar0_buf + pos, buf, count)) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		if (common)
+			ret = virtio_pci_admin_legacy_common_io_write(pdev, pos,
+					count, bar0_buf + pos);
+		else
+			ret = virtio_pci_admin_legacy_device_io_write(pdev, 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;
+		} else {
+			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_legacy_rw_cmd(virtvdev, pos, buf, count,
+						   read);
+	}
+
+	return ret ? ret : count;
+}
+
+static bool range_intersect_range(loff_t range1_start, size_t count1,
+				  loff_t range2_start, size_t count2,
+				  loff_t *start_offset,
+				  size_t *intersect_count,
+				  size_t *register_offset)
+{
+	if (range1_start <= range2_start &&
+	    range1_start + count1 > range2_start) {
+		*start_offset = range2_start - range1_start;
+		*intersect_count = min_t(size_t, count2,
+					 range1_start + count1 - range2_start);
+		*register_offset = 0;
+		return true;
+	}
+
+	if (range1_start > range2_start &&
+	    range1_start < range2_start + count2) {
+		*start_offset = 0;
+		*intersect_count = min_t(size_t, count1,
+					 range2_start + count2 - range1_start);
+		*register_offset = range1_start - range2_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;
+	size_t register_offset;
+	loff_t copy_offset;
+	size_t copy_count;
+	__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_intersect_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
+				  &copy_offset, &copy_count, &register_offset)) {
+		val16 = cpu_to_le16(VIRTIO_TRANS_ID_NET);
+		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset, copy_count))
+			return -EFAULT;
+	}
+
+	if ((le16_to_cpu(virtvdev->pci_cmd) & PCI_COMMAND_IO) &&
+	    range_intersect_range(pos, count, PCI_COMMAND, sizeof(val16),
+				  &copy_offset, &copy_count, &register_offset)) {
+		if (copy_from_user((void *)&val16 + register_offset, buf + copy_offset,
+				   copy_count))
+			return -EFAULT;
+		val16 |= cpu_to_le16(PCI_COMMAND_IO);
+		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset,
+				 copy_count))
+			return -EFAULT;
+	}
+
+	if (range_intersect_range(pos, count, PCI_REVISION_ID, sizeof(val8),
+				  &copy_offset, &copy_count, &register_offset)) {
+		/* Transional needs to have revision 0 */
+		val8 = 0;
+		if (copy_to_user(buf + copy_offset, &val8, copy_count))
+			return -EFAULT;
+	}
+
+	if (range_intersect_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
+				  &copy_offset, &copy_count, &register_offset)) {
+		u8 log_bar_size = ilog2(roundup_pow_of_two(virtvdev->bar0_virtual_buf_size));
+		u32 mask_size = ~((BIT(log_bar_size) - 1));
+		u32 pci_base_addr_0 = le32_to_cpu(virtvdev->pci_base_addr_0);
+
+		val32 = cpu_to_le32((pci_base_addr_0 & mask_size) | PCI_BASE_ADDRESS_SPACE_IO);
+		if (copy_to_user(buf + copy_offset, (void *)&val32 + register_offset, copy_count))
+			return -EFAULT;
+	}
+
+	if (range_intersect_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
+				  &copy_offset, &copy_count, &register_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, (void *)&val16 + register_offset,
+				 copy_count))
+			return -EFAULT;
+	}
+
+	if (range_intersect_range(pos, count, PCI_SUBSYSTEM_VENDOR_ID, sizeof(val16),
+				  &copy_offset, &copy_count, &register_offset)) {
+		val16 = cpu_to_le16(PCI_VENDOR_ID_REDHAT_QUMRANET);
+		if (copy_to_user(buf + copy_offset, (void *)&val16 + register_offset,
+				 copy_count))
+			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) {
+		size_t register_offset;
+		loff_t copy_offset;
+		size_t copy_count;
+
+		if (range_intersect_range(pos, count, PCI_COMMAND, sizeof(virtvdev->pci_cmd),
+					  &copy_offset, &copy_count,
+					  &register_offset)) {
+			if (copy_from_user((void *)&virtvdev->pci_cmd + register_offset,
+					   buf + copy_offset,
+					   copy_count))
+				return -EFAULT;
+		}
+
+		if (range_intersect_range(pos, count, PCI_BASE_ADDRESS_0,
+					  sizeof(virtvdev->pci_base_addr_0),
+					  &copy_offset, &copy_count,
+					  &register_offset)) {
+			if (copy_from_user((void *)&virtvdev->pci_base_addr_0 + register_offset,
+					   buf + copy_offset,
+					   copy_count))
+				return -EFAULT;
+		}
+	}
+
+	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 int virtiovf_get_device_config_size(unsigned short device)
+{
+	/* Network card */
+	return offsetofend(struct virtio_net_config, status);
+}
+
+static int virtiovf_read_notify_info(struct virtiovf_pci_core_device *virtvdev)
+{
+	u64 offset;
+	int ret;
+	u8 bar;
+
+	ret = virtio_pci_admin_legacy_io_notify_info(virtvdev->core_device.pdev,
+				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;
+	ret = virtiovf_read_notify_info(virtvdev);
+	if (ret)
+		return ret;
+
+	/* Being ready with a buffer that supports MSIX */
+	virtvdev->bar0_virtual_buf_size = VIRTIO_PCI_CONFIG_OFF(true) +
+				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-vfio-pci-trans",
+	.init = virtiovf_pci_init_device,
+	.release = virtiovf_pci_core_release_dev,
+	.open_device = virtiovf_pci_open_device,
+	.close_device = vfio_pci_core_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_vfio_pci_ops = {
+	.name = "virtio-vfio-pci",
+	.init = vfio_pci_core_init_dev,
+	.release = vfio_pci_core_release_dev,
+	.open_device = virtiovf_pci_open_device,
+	.close_device = vfio_pci_core_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;
+}
+
+static int virtiovf_pci_probe(struct pci_dev *pdev,
+			      const struct pci_device_id *id)
+{
+	const struct vfio_device_ops *ops = &virtiovf_vfio_pci_ops;
+	struct virtiovf_pci_core_device *virtvdev;
+	int ret;
+
+	if (pdev->is_virtfn && virtio_pci_admin_has_legacy_io(pdev) &&
+	    !virtiovf_bar0_exists(pdev))
+		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[] = {
+	/* Only virtio-net is supported/tested so far */
+	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1041) },
+	{}
+};
+
+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 <[e-mail]>");
+MODULE_DESCRIPTION(
+	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO NET devices");