[Questions] non-shared disk migration: jobs abort and bandwidth

[Han Han <hhan@xxxxxxxxxx>]

Hi developers,

Recently, I am researching migration with non-share disk(flags VIR_MIGRATE_NON_SHARED_DISK and VIR_MIGRATE_NON_SHARED_INC).

As we know, the non-shared disk migration could have block jobs to copy the disk image from the src host to the dst host. So here are my questions for non-shared disk migration:

q1. For the API virDomainMigrate3 with the bandwidth param, could it set the bandwidth of block jobs?

q2. For the API virDomainMigrateSetMaxSpeed, could it set the bandwidth of block jobs?

q3. For the domain job abort API virDomainAbortJob, could it stop the block job of non-shared disk migration?

q4. For the block job bandwidth API virDomainBlockJobSetSpeed, could it set the block job of non-shared disk migration?

q5. For the block job abort API virDomainBlockJobAbort, could it stop the block job of non-shared disk migration?

Then I got the test results of libvirt-8.4.0-1.el9.x86_64 qemu-kvm-7.0.0-4.el9.x86_64:

q1: The bandwidth limit of virDomainMigrate3 is effective to the blockjob:

➜  ~ virsh migrate OVMF qemu+ssh://root@hhan-rhel9--1/system --live --p2p --tls --tls-destination hhan-rhel9--1 --copy-storage-all --disks-uri tcp://hhan-rhel9--1:49156 --bandwidth 2

➜  ~ virsh blockjob OVMF vda                                                
Block Copy: [  0 %]    Bandwidth limit: 2097152 bytes/s (2.000 MiB/s)

q2: The virDomainMigrateSetMaxSpeed doesn't change the the bandwidth of block jobs.

➜  ~ virsh migrate-setspeed OVMF 8          

➜  ~ virsh blockjob OVMF vda      
Block Copy: [  9 %]    Bandwidth limit: 2097152 bytes/s (2.000 MiB/s)

q3: The virDomainAbortJob could stop a block job of non-shared disk migration

➜  ~ virsh migrate OVMF qemu+ssh://root@hhan-rhel9--1/system --live --p2p --tls --tls-destination hhan-rhel9--1 --copy-storage-all --disks-uri tcp://hhan-rhel9--1:49156 --bandwidth 2

Then start a virsh event on another terminal:

➜  ~ virsh event --loop --all

Abort the domain job:

➜  ~ virsh domjobabort OVMF

The error "error: operation aborted: migration out: canceled by client" appears at the terminal of "virsh migrate"

The terminal of "virsh event" shows the block job has been failed:
event 'block-job' for domain 'OVMF': Block Copy for /var/lib/libvirt/images/OVMF.qcow2 failed
event 'block-job-2' for domain 'OVMF': Block Copy for vda failed

q4: The block job bandwidth of non-shared disk migration cannot be set by virDomainBlockJobSetSpeed:

➜  ~ virsh blockjob OVMF vda --bandwidth 10
error: Timed out during operation: cannot acquire state change lock (held by monitor=remoteDispatchDomainMigratePerform3Params)

q5: The block job of non-shared disk migration cannot be aborted by virDomainBlockJobAbort:

➜  ~ virsh blockjob OVMF vda --abort      
error: Timed out during operation: cannot acquire state change lock (held by monitor=remoteDispatchDomainMigratePerform3Params)

Are the results above expected?

Here are my personal thoughts:

For the bandwidth in q1 and q2, they are commented as migration bandwidth(https://gitlab.com/libvirt/libvirt/-/blob/master/include/libvirt/libvirt-domain.h#L1165 , https://gitlab.com/libvirt/libvirt/-/blob/master/src/libvirt-domain.c#L9696 ), but one works for block jobs while one doesn't. So we should make the comment clear whether they are the bandwidth of VM migration or the bandwidth of migration with blockjobs. What's more, add a flag to virDomainMigrateMaxSpeedFlags to support set bandwidth to the blockjobs in migration.

For q4 and q5, if we will not support to change the block job of non-shared disk migration by blockjob APIs, we should note that in the migration doc or the block job doc, to present the difference between this type of block job and the others.