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Pull VFIO updates from Alex Williamson: - Remove redundant resource check in vfio-platform (Angus Chen) - Use GFP_KERNEL_ACCOUNT for persistent userspace allocations, allowing removal of arbitrary kernel limits in favor of cgroup control (Yishai Hadas) - mdev tidy-ups, including removing the module-only build restriction for sample drivers, Kconfig changes to select mdev support, documentation movement to keep sample driver usage instructions with sample drivers rather than with API docs, remove references to out-of-tree drivers in docs (Christoph Hellwig) - Fix collateral breakages from mdev Kconfig changes (Arnd Bergmann) - Make mlx5 migration support match device support, improve source and target flows to improve pre-copy support and reduce downtime (Yishai Hadas) - Convert additional mdev sysfs case to use sysfs_emit() (Bo Liu) - Resolve copy-paste error in mdev mbochs sample driver Kconfig (Ye Xingchen) - Avoid propagating missing reset error in vfio-platform if reset requirement is relaxed by module option (Tomasz Duszynski) - Range size fixes in mlx5 variant driver for missed last byte and stricter range calculation (Yishai Hadas) - Fixes to suspended vaddr support and locked_vm accounting, excluding mdev configurations from the former due to potential to indefinitely block kernel threads, fix underflow and restore locked_vm on new mm (Steve Sistare) - Update outdated vfio documentation due to new IOMMUFD interfaces in recent kernels (Yi Liu) - Resolve deadlock between group_lock and kvm_lock, finally (Matthew Rosato) - Fix NULL pointer in group initialization error path with IOMMUFD (Yan Zhao) * tag 'vfio-v6.3-rc1' of https://github.com/awilliam/linux-vfio: (32 commits) vfio: Fix NULL pointer dereference caused by uninitialized group->iommufd docs: vfio: Update vfio.rst per latest interfaces vfio: Update the kdoc for vfio_device_ops vfio/mlx5: Fix range size calculation upon tracker creation vfio: no need to pass kvm pointer during device open vfio: fix deadlock between group lock and kvm lock vfio: revert "iommu driver notify callback" vfio/type1: revert "implement notify callback" vfio/type1: revert "block on invalid vaddr" vfio/type1: restore locked_vm vfio/type1: track locked_vm per dma vfio/type1: prevent underflow of locked_vm via exec() vfio/type1: exclude mdevs from VFIO_UPDATE_VADDR vfio: platform: ignore missing reset if disabled at module init vfio/mlx5: Improve the target side flow to reduce downtime vfio/mlx5: Improve the source side flow upon pre_copy vfio/mlx5: Check whether VF is migratable samples: fix the prompt about SAMPLE_VFIO_MDEV_MBOCHS vfio/mdev: Use sysfs_emit() to instead of sprintf() vfio-mdev: add back CONFIG_VFIO dependency ...
Using the mtty vfio-mdev sample code
====================================
mtty is a sample vfio-mdev driver that demonstrates how to use the mediated
device framework.
The sample driver creates an mdev device that simulates a serial port over a PCI
card.
1. Build and load the mtty.ko module.
This step creates a dummy device, /sys/devices/virtual/mtty/mtty/
Files in this device directory in sysfs are similar to the following::
# tree /sys/devices/virtual/mtty/mtty/
/sys/devices/virtual/mtty/mtty/
|-- mdev_supported_types
| |-- mtty-1
| | |-- available_instances
| | |-- create
| | |-- device_api
| | |-- devices
| | `-- name
| `-- mtty-2
| |-- available_instances
| |-- create
| |-- device_api
| |-- devices
| `-- name
|-- mtty_dev
| `-- sample_mtty_dev
|-- power
| |-- autosuspend_delay_ms
| |-- control
| |-- runtime_active_time
| |-- runtime_status
| `-- runtime_suspended_time
|-- subsystem -> ../../../../class/mtty
`-- uevent
2. Create a mediated device by using the dummy device that you created in the
previous step::
# echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" > \
/sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create
3. Add parameters to qemu-kvm::
-device vfio-pci,\
sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
4. Boot the VM.
In the Linux guest VM, with no hardware on the host, the device appears
as follows::
# lspci -s 00:05.0 -xxvv
00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])
Subsystem: Device 4348:3253
Physical Slot: 5
Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx-
Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
Interrupt: pin A routed to IRQ 10
Region 0: I/O ports at c150 [size=8]
Region 1: I/O ports at c158 [size=8]
Kernel driver in use: serial
00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00
10: 51 c1 00 00 59 c1 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 48 43 53 32
30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 00 00
In the Linux guest VM, dmesg output for the device is as follows:
serial 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ 10
0000:00:05.0: ttyS1 at I/O 0xc150 (irq = 10) is a 16550A
0000:00:05.0: ttyS2 at I/O 0xc158 (irq = 10) is a 16550A
5. In the Linux guest VM, check the serial ports::
# setserial -g /dev/ttyS*
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0xc150, IRQ: 10
/dev/ttyS2, UART: 16550A, Port: 0xc158, IRQ: 10
6. Using minicom or any terminal emulation program, open port /dev/ttyS1 or
/dev/ttyS2 with hardware flow control disabled.
7. Type data on the minicom terminal or send data to the terminal emulation
program and read the data.
Data is loop backed from hosts mtty driver.
8. Destroy the mediated device that you created::
# echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001/remove