On Sun, Jun 30, 2024 at 12:44:02PM -0700, Steve Sistare wrote: > What? > > This patch series adds the live migration cpr-transfer mode, which > allows the user to transfer a guest to a new QEMU instance on the same > host. It is identical to cpr-exec in most respects, except as described > below.
I definitely prefer this one more than the exec solution, thanks for trying this out. It's a matter of whether we'll need both, my answer would be no.. > > The new user-visible interfaces are: > * cpr-transfer (MigMode migration parameter) > * cpr-uri (migration parameter) I wonder whether this parameter can be avoided already, maybe we can let cpr-transfer depend on unix socket in -incoming, then integrate fd sharing in the same channel? > * cpr-uri (command-line argument) > > In this mode, the user starts new QEMU on the same host as old QEMU, with > the same arguments as old QEMU, plus the -incoming and the -cpr-uri options. > The user issues the migrate command to old QEMU, which stops the VM, saves > state to the migration channels, and enters the postmigrate state. Execution > resumes in new QEMU. > > This mode requires a second migration channel, specified by the cpr-uri > migration property on the outgoing side, and by the cpr-uri QEMU command-line > option on the incoming side. The channel must be a type, such as unix socket, > that supports SCM_RIGHTS. > > This series depends on the series "Live update: cpr-exec mode". > > Why? > > cpr-transfer offers the same benefits as cpr-exec mode, but with a model > for launching new QEMU that may be more natural for some management packages. > > How? > > The file descriptors are kept open by sending them to new QEMU via the > cpr-uri, which must support SCM_RIGHTS. > > Example: > > In this example, we simply restart the same version of QEMU, but in > a real scenario one would use a new QEMU binary path in terminal 2. > > Terminal 1: start old QEMU > # qemu-kvm -monitor stdio -object > memory-backend-file,id=ram0,size=4G,mem-path=/dev/shm/ram0,share=on > -m 4G -machine anon-alloc=memfd ... > > Terminal 2: start new QEMU > # qemu-kvm ... -incoming unix:vm.sock -cpr-uri unix:cpr.sock > > Terminal 1: > QEMU 9.1.50 monitor - type 'help' for more information > (qemu) info status > VM status: running > (qemu) migrate_set_parameter mode cpr-transfer > (qemu) migrate_set_parameter cpr-uri unix:cpr.sock > (qemu) migrate -d unix:vm.sock > (qemu) info status > VM status: paused (postmigrate) > > Terminal 2: > QEMU 9.1.50 monitor - type 'help' for more information > (qemu) info status > VM status: running > > Steve Sistare (6): > migration: SCM_RIGHTS for QEMUFile > migration: VMSTATE_FD > migration: cpr-transfer save and load > migration: cpr-uri parameter > migration: cpr-uri option > migration: cpr-transfer mode > > include/migration/cpr.h | 4 ++ > include/migration/vmstate.h | 9 +++++ > migration/cpr-transfer.c | 81 +++++++++++++++++++++++++++++++++++++++++ > migration/cpr.c | 16 +++++++- > migration/meson.build | 1 + > migration/migration-hmp-cmds.c | 10 +++++ > migration/migration.c | 37 +++++++++++++++++++ > migration/options.c | 29 +++++++++++++++ > migration/options.h | 1 + > migration/qemu-file.c | 83 > ++++++++++++++++++++++++++++++++++++++++-- > migration/qemu-file.h | 2 + > migration/ram.c | 1 + > migration/trace-events | 2 + > migration/vmstate-types.c | 33 +++++++++++++++++ > qapi/migration.json | 38 ++++++++++++++++++- > qemu-options.hx | 8 ++++ > stubs/vmstate.c | 7 ++++ > system/vl.c | 3 ++ > 18 files changed, 359 insertions(+), 6 deletions(-) > create mode 100644 migration/cpr-transfer.c > > -- > 1.8.3.1 > -- Peter Xu
