mirror of
https://github.com/cloud-hypervisor/cloud-hypervisor.git
synced 2024-12-24 22:55:19 +00:00
57 lines
2.3 KiB
Markdown
57 lines
2.3 KiB
Markdown
|
# Cloud Hypervisor Hot Plug
|
||
|
|
|
||
|
|
Currently Cloud Hypervisor only support hot plugging of CPU devices.
|
||
|
|
|
||
|
|
## Kernel support
|
||
|
|
|
||
|
|
For hotplug on Cloud Hypervisor ACPI GED support is needed. This can either be achieved by turning on `CONFIG_ACPI_REDUCED_HARDWARE_ONLY`
|
||
|
|
or by using this kernel patch (available in 5.5rc1 and later): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/drivers/acpi/Makefile?id=ac36d37e943635fc072e9d4f47e40a48fbcdb3f0
|
||
|
|
|
||
|
|
This patch is integrated into the Clear Linux KVM and cloudguest images.
|
||
|
|
|
||
|
|
## CPU Hot Plug
|
||
|
|
|
||
|
|
Extra vCPUs can be added (but not removed [1]) from a running Cloud Hypervisor instance. This is controlled by two mechanisms:
|
||
|
|
|
||
|
|
1. Specifying a number of maximum potential vCPUs that is greater than the number of default (boot) vCPUs.
|
||
|
|
2. Making a HTTP API request to the VM to ask for the additional vCPUs to be added.
|
||
|
|
|
||
|
|
To use CPU hotplug start the VM with the number of max vCPUs greater than the number of boot vCPUs, e.g.
|
||
|
|
|
||
|
|
```shell
|
||
|
|
$ pushd $CLOUDH
|
||
|
|
$ sudo setcap cap_net_admin+ep ./cloud-hypervisor/target/release/cloud-hypervisor
|
||
|
|
$ ./cloud-hypervisor/target/release/cloud-hypervisor \
|
||
|
|
--kernel ./hypervisor-fw \
|
||
|
|
--disk path=clear-31890-kvm.img \
|
||
|
|
--cpus boot=4,max=8 \
|
||
|
|
--memory size=1024M \
|
||
|
|
--net "tap=,mac=,ip=,mask=" \
|
||
|
|
--rng \
|
||
|
|
--api-socket=/tmp/ch-socket
|
||
|
|
$ popd
|
||
|
|
```
|
||
|
|
|
||
|
|
Notice the addition of `--api-socket=/tmp/ch-socket` and a `max` parameter on `--cpus boot=4.max=8`.
|
||
|
|
|
||
|
|
To ask the VMM to add additional vCPUs then use the resize API:
|
||
|
|
|
||
|
|
```shell
|
||
|
|
curl -H "Accept: application/json" -H "Content-Type: application/json" -i -XPUT --unix-socket /tmp/ch-socket -d "{ \"desired_vcpus\":8}" http://localhost/api/v1/vm.resize
|
||
|
|
```
|
||
|
|
|
||
|
|
The extra vCPU threads will be created and advertised to the running kernel. The kernel does not bring up the CPUs immediately and instead the user must "on-line" them from inside the VM:
|
||
|
|
|
||
|
|
```shell
|
||
|
|
root@ch-guest ~ # lscpu | grep list:
|
||
|
|
On-line CPU(s) list: 0-3
|
||
|
|
Off-line CPU(s) list: 4-7
|
||
|
|
root@ch-guest ~ # echo 1 | tee /sys/devices/system/cpu/cpu[4,5,6,7]/online
|
||
|
|
1
|
||
|
|
root@ch-guest ~ # lscpu | grep list:
|
||
|
|
On-line CPU(s) list: 0-7
|
||
|
|
```
|
||
|
|
|
||
|
|
After a reboot the added CPUs will remain.
|
||
|
|
|
||
|
|
[1]: It is not currently possible to remove CPUs after they are added however CPU hot unplug is included in our roadmap for a future version.
|