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.
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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
Reviewed-by: Jason Gunthorpe <j...@nvidia.com>
Signed-off-by: Yishai Hadas <yish...@nvidia.com>
---
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 | 567 +++++++++++++++++++++++++++++++
6 files changed, 598 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 012df8ccf34e..b246b769092d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22872,6 +22872,13 @@ 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
+L: virtualizat...@lists.linux-foundation.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..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.
