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eb61eca0e8
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.
In addition, any data path read/write access (i.e. virtio driver
notifications) will be captured by the driver and 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]
03c2d32e50
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20231219093247.170936-10-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
71 lines
1.8 KiB
Plaintext
71 lines
1.8 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menu "VFIO support for PCI devices"
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depends on PCI && MMU
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config VFIO_PCI_CORE
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tristate
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select VFIO_VIRQFD
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select IRQ_BYPASS_MANAGER
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config VFIO_PCI_MMAP
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def_bool y if !S390
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depends on VFIO_PCI_CORE
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config VFIO_PCI_INTX
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def_bool y if !S390
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depends on VFIO_PCI_CORE
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config VFIO_PCI
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tristate "Generic VFIO support for any PCI device"
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select VFIO_PCI_CORE
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help
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Support for the generic PCI VFIO bus driver which can connect any
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PCI device to the VFIO framework.
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If you don't know what to do here, say N.
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if VFIO_PCI
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config VFIO_PCI_VGA
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bool "Generic VFIO PCI support for VGA devices"
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depends on X86 && VGA_ARB
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help
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Support for VGA extension to VFIO PCI. This exposes an additional
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region on VGA devices for accessing legacy VGA addresses used by
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BIOS and generic video drivers.
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If you don't know what to do here, say N.
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config VFIO_PCI_IGD
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bool "Generic VFIO PCI extensions for Intel graphics (GVT-d)"
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depends on X86
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default y
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help
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Support for Intel IGD specific extensions to enable direct
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assignment to virtual machines. This includes exposing an IGD
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specific firmware table and read-only copies of the host bridge
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and LPC bridge config space.
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To enable Intel IGD assignment through vfio-pci, say Y.
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endif
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config VFIO_PCI_ZDEV_KVM
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bool "VFIO PCI extensions for s390x KVM passthrough"
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depends on S390 && KVM
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default y
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help
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Support s390x-specific extensions to enable support for enhancements
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to KVM passthrough capabilities, such as interpretive execution of
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zPCI instructions.
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To enable s390x KVM vfio-pci extensions, say Y.
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source "drivers/vfio/pci/mlx5/Kconfig"
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source "drivers/vfio/pci/hisilicon/Kconfig"
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source "drivers/vfio/pci/pds/Kconfig"
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source "drivers/vfio/pci/virtio/Kconfig"
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endmenu
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