mirror of
https://github.com/cloud-hypervisor/cloud-hypervisor.git
synced 2024-11-05 11:31:14 +00:00
169a6bb83b
Since INTx is now supported for VFIO PCI devices, there is no more limitations regarding VFIO, which means the documentation must be updated accordingly. Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
81 lines
2.5 KiB
Markdown
81 lines
2.5 KiB
Markdown
# Cloud Hypervisor VFIO HOWTO
|
|
|
|
VFIO (Virtual Function I/O) is a kernel framework that exposes direct device
|
|
access to userspace. `cloud-hypervisor`, as many VMMs do, uses the VFIO
|
|
framework to directly assign host physical devices to the guest workloads.
|
|
|
|
## Direct Device Assignment with Cloud Hypervisor
|
|
|
|
To assign a device to a `cloud-hypervisor` guest, the device needs to be managed
|
|
by the VFIO kernel drivers. However, by default, a host device will be bound to
|
|
its native driver, which is not the VFIO one.
|
|
|
|
As a consequence, a device must be unbound from its native driver before passing
|
|
it to `cloud-hypervisor` for assigning it to a guess.
|
|
|
|
### Example
|
|
|
|
In this example we're going to assign a PCI memory card (SD, MMC, etc) reader
|
|
from the host in a cloud hypervisor guest.
|
|
|
|
`cloud-hypervisor` only supports assigning PCI devices to its guests. `lspci`
|
|
helps with identifying PCI devices on the host:
|
|
|
|
```
|
|
$ lspci
|
|
[...]
|
|
01:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
|
|
[...]
|
|
```
|
|
|
|
Here we see that our device is on bus 1, slot 0 and function 0 (`01:00.0`).
|
|
|
|
Now that we have identified the device, we must unbind it from its native driver
|
|
(`rtsx_pci`) and bind it to the VFIO driver instead (`vfio_pci`).
|
|
|
|
First we add VFIO support to the host:
|
|
|
|
```
|
|
$ sudo modprobe vfio_pci
|
|
$ sudo modprobe vfio_iommu_type1 allow_unsafe_interrupts
|
|
```
|
|
|
|
Then we unbind it from its native driver:
|
|
|
|
```
|
|
$ echo 0000:01:00.0 > /sys/bus/pci/devices/0000\:01\:00.0/driver/unbind
|
|
```
|
|
|
|
And finally we bind it to the VFIO driver. To do that we first need to get the
|
|
device's VID (Vendor ID) and PID (Product ID):
|
|
|
|
```
|
|
$ lspci -n -s 01:00.0
|
|
01:00.0 ff00: 10ec:525a (rev 01)
|
|
|
|
$ echo 10ec 525a > /sys/bus/pci/drivers/vfio-pci/new_id
|
|
```
|
|
|
|
Now the device is managed by the VFIO framework.
|
|
|
|
The final step is to give that device to `cloud-hypervisor` to assign it to the
|
|
guest. This is done by using the `--device` command line option. This option
|
|
takes the device's sysfs path as an argument. In our example it is
|
|
`/sys/bus/pci/devices/0000:01:00.0/`:
|
|
|
|
```
|
|
./target/debug/cloud-hypervisor \
|
|
--kernel ~/vmlinux \
|
|
--disk path=~/focal-server-cloudimg-amd64.raw \
|
|
--console off \
|
|
--serial tty \
|
|
--cmdline "console=ttyS0 root=/dev/vda1 rw" \
|
|
--cpus 4 \
|
|
--memory size=512M \
|
|
--device path=/sys/bus/pci/devices/0000:01:00.0/
|
|
```
|
|
|
|
The guest kernel will then detect the card reader on its PCI bus and provided
|
|
that support for this device is enabled, it will probe and enable it for the
|
|
guest to use.
|