Add a mode migration parameter that can be used to select alternate migration algorithms. The default mode is normal, representing the current migration algorithm, and does not need to be explicitly set.
Provide the cpr-reboot (CheckPoint and Restart) migration mode for live update, which saves state to a file. This allows one to quit qemu, reboot to an updated kernel, install an updated version of qemu, and resume via the migrate-incoming command. The caller must specify a migration URI that writes to and reads from a file, and must set the mode parameter before invoking the migrate or migrate-incoming commands. Unlike normal mode, the use of certain local storage options does not block cpr-reboot mode, but the caller must not modify guest block devices between the quit and restart. To avoid saving guest RAM to the state file, the memory backend must be shared, and the @x-ignore-shared migration capability must be set. Guest RAM must be non-volatile across reboot, which can be achieved by backing it with a dax device, or /dev/shm PKRAM as proposed in https://lore.kernel.org/lkml/1617140178-8773-1-git-send-email-anthony.yzn...@oracle.com but this is not enforced. The restarted qemu arguments must match those used to initially start qemu, plus the -incoming option. This patch series contains minimal functionality. Future patches will enhance reboot mode by preserving vfio devices for suspended guests. They will also add a new mode for updating qemu using the exec system call, which will keep vfio devices and certain character devices alive. Here is an example of updating the host kernel using reboot mode. window 1 | window 2 | # qemu-system-$arch -monitor stdio | mem-path=/dev/dax0.0 ... | QEMU 8.1.50 monitor - type 'help' for more info | (qemu) info status | VM status: running | | # yum update kernel-uek (qemu) migrate_set_capability x-ignore-shared on| (qemu) migrate_set_parameter mode cpr-reboot | (qemu) migrate -d file:vm.state | (qemu) info status | VM status: paused (postmigrate) | (qemu) quit | | # systemctl kexec | kexec_core: Starting new kernel | ... | | # qemu-system-$arch -monitor stdio | mem-path=/dev/dax0.0 -incoming defer ... | QEMU 8.1.50 monitor - type 'help' for more info | (qemu) info status | VM status: paused (inmigrate) | (qemu) migrate_set_capability x-ignore-shared on| (qemu) migrate_set_parameter mode cpr-reboot | (qemu) migrate_incoming file:vm.state | (qemu) info status | VM status: running | Changes in V2: - moved "migration mode" code and comments to more appropriate places - clarified the behavior of non-shared-memory backends - split blocker patches and reverted some blockers - added a test Steve Sistare (6): migration: mode parameter migration: per-mode blockers cpr: relax blockdev migration blockers cpr: relax vhost migration blockers cpr: reboot mode tests/qtest: migration: add reboot mode test block/parallels.c | 2 +- block/qcow.c | 2 +- block/vdi.c | 2 +- block/vhdx.c | 2 +- block/vmdk.c | 2 +- block/vpc.c | 2 +- block/vvfat.c | 2 +- hw/core/qdev-properties-system.c | 14 ++++++ hw/scsi/vhost-scsi.c | 2 +- hw/virtio/vhost.c | 2 +- include/hw/qdev-properties-system.h | 4 ++ include/migration/blocker.h | 44 +++++++++++++++-- include/migration/misc.h | 1 + migration/migration-hmp-cmds.c | 9 ++++ migration/migration.c | 95 ++++++++++++++++++++++++++++++++----- migration/options.c | 21 ++++++++ migration/options.h | 1 + qapi/migration.json | 40 ++++++++++++++-- stubs/migr-blocker.c | 10 ++++ tests/qtest/migration-test.c | 27 +++++++++++ 20 files changed, 255 insertions(+), 29 deletions(-) -- 1.8.3.1
