Hi Steve On Tue, Jul 6, 2021 at 8:58 PM Steve Sistare <steven.sist...@oracle.com> wrote:
> Provide the cprsave, cprexec, and cprload commands for live update. These > save and restore VM state, with minimal guest pause time, so that qemu may > be updated to a new version in between. > > cprsave stops the VM and saves vmstate to an ordinary file. It supports > any > type of guest image and block device, but the caller must not modify guest > block devices between cprsave and cprload. It supports two modes: reboot > and restart. > > In reboot mode, the caller invokes cprsave and then terminates qemu. > The caller may then update the host kernel and system software and reboot. > The caller resumes the guest by running qemu with the same arguments as the > original process and invoking cprload. To use this mode, guest ram must be > mapped to a persistent shared memory file such as /dev/dax0.0, or /dev/shm > PKRAM as proposed in > https://lore.kernel.org/lkml/1617140178-8773-1-git-send-email-anthony.yzn...@oracle.com > . > > The reboot mode supports vfio devices if the caller first suspends the > guest, such as by issuing guest-suspend-ram to the qemu guest agent. The > guest drivers' suspend methods flush outstanding requests and re-initialize > the devices, and thus there is no device state to save and restore. > > Restart mode preserves the guest VM across a restart of the qemu process. > After cprsave, the caller passes qemu command-line arguments to cprexec, > which directly exec's the new qemu binary. The arguments must include -S > so new qemu starts in a paused state and waits for the cprload command. > The restart mode supports vfio devices by preserving the vfio container, > group, device, and event descriptors across the qemu re-exec, and by > updating DMA mapping virtual addresses using VFIO_DMA_UNMAP_FLAG_VADDR and > VFIO_DMA_MAP_FLAG_VADDR as defined in > https://lore.kernel.org/kvm/1611939252-7240-1-git-send-email-steven.sist...@oracle.com/ > and integrated in Linux kernel 5.12. > > To use the restart mode, qemu must be started with the memfd-alloc option, > which allocates guest ram using memfd_create. The memfd's are saved to > the environment and kept open across exec, after which they are found from > the environment and re-mmap'd. Hence guest ram is preserved in place, > albeit with new virtual addresses in the qemu process. > > The caller resumes the guest by invoking cprload, which loads state from > the file. If the VM was running at cprsave time, then VM execution > resumes. > If the VM was suspended at cprsave time (reboot mode), then the caller must > issue a system_wakeup command to resume. > > The first patches add reboot mode: > - qemu_ram_volatile > - cpr: reboot mode > - cpr: QMP interfaces for reboot > - cpr: HMP interfaces for reboot > > The next patches add restart mode: > - as_flat_walk > - oslib: qemu_clr_cloexec > - machine: memfd-alloc option > - vl: add helper to request re-exec > - string to strList > - util: env var helpers > - cpr: restart mode > - cpr: QMP interfaces for restart > - cpr: HMP interfaces for restart > > The next patches add vfio support for restart mode: > - pci: export functions for cpr > - vfio-pci: refactor for cpr > - vfio-pci: cpr part 1 > - vfio-pci: cpr part 2 > > The next patches preserve various descriptor-based backend devices across > cprexec: > - vhost: reset vhost devices upon cprsave > - hostmem-memfd: cpr support > - chardev: cpr framework > - chardev: cpr for simple devices > - chardev: cpr for pty > - chardev: cpr for sockets > - cpr: only-cpr-capable option > - simplify savevm > > Here is an example of updating qemu from v4.2.0 to v4.2.1 using > restart mode. The software update is performed while the guest is > running to minimize downtime. > > window 1 | window 2 > | > # qemu-system-x86_64 ... | > QEMU 4.2.0 monitor - type 'help' ... | > (qemu) info status | > VM status: running | > | # yum update qemu > (qemu) cprsave /tmp/qemu.sav restart | > (qemu) cprexec qemu-system-x86_64 -S ... | > QEMU 4.2.1 monitor - type 'help' ... | > (qemu) info status | > VM status: paused (prelaunch) | > (qemu) cprload /tmp/qemu.sav | > (qemu) info status | > VM status: running | > > > Here is an example of updating the host kernel using reboot mode. > > window 1 | window 2 > | > # qemu-system-x86_64 ...mem-path=/dev/dax0.0 ...| > QEMU 4.2.1 monitor - type 'help' ... | > (qemu) info status | > VM status: running | > | # yum update kernel-uek > (qemu) cprsave /tmp/qemu.sav restart | > (qemu) quit | > | > # systemctl kexec | > kexec_core: Starting new kernel | > ... | > | > # qemu-system-x86_64 -S mem-path=/dev/dax0.0 ...| > QEMU 4.2.1 monitor - type 'help' ... | > (qemu) info status | > VM status: paused (prelaunch) | > (qemu) cprload /tmp/qemu.sav | > (qemu) info status | > VM status: running | > > Changes from V1 to V2: > - revert vmstate infrastructure changes > - refactor cpr functions into new files > - delete MADV_DOEXEC and use memfd + VFIO_DMA_UNMAP_FLAG_SUSPEND to > preserve memory. > - add framework to filter chardev's that support cpr > - save and restore vfio eventfd's > - modify cprinfo QMP interface > - incorporate misc review feedback > - remove unrelated and unneeded patches > - refactor all patches into a shorter and easier to review series > > Changes from V2 to V3: > - rebase to qemu 6.0.0 > - use final definition of vfio ioctls (VFIO_DMA_UNMAP_FLAG_VADDR etc) > - change memfd-alloc to a machine option > - Use qio_channel_socket_new_fd instead of adding > qio_channel_socket_new_fd > - close monitor socket during cpr > - fix a few unreported bugs > - support memory-backend-memfd > > Changes from V3 to V4: > - split reboot mode into separate patches > - add cprexec command > - delete QEMU_START_FREEZE, argv_main, and /usr/bin/qemu-exec > - add more checks for vfio and cpr compatibility, and recover after > errors > - save vfio pci config in vmstate > - rename {setenv,getenv}_event_fd to {save,load}_event_fd > - use qemu_strtol > - change 6.0 references to 6.1 > - use strerror(), use EXIT_FAILURE, remove period from error messages > - distribute MAINTAINERS additions to each patch > > Steve Sistare (21): > qemu_ram_volatile > cpr: reboot mode > as_flat_walk > oslib: qemu_clr_cloexec > machine: memfd-alloc option > vl: add helper to request re-exec > string to strList > util: env var helpers > cpr: restart mode > cpr: QMP interfaces for restart > cpr: HMP interfaces for restart > pci: export functions for cpr > vfio-pci: refactor for cpr > vfio-pci: cpr part 1 > vfio-pci: cpr part 2 > hostmem-memfd: cpr support > chardev: cpr framework > chardev: cpr for simple devices > chardev: cpr for pty > cpr: only-cpr-capable option > simplify savevm > > Mark Kanda, Steve Sistare (4): > cpr: QMP interfaces for reboot > cpr: HMP interfaces for reboot > vhost: reset vhost devices upon cprsave > chardev: cpr for sockets > > MAINTAINERS | 12 +++ > backends/hostmem-memfd.c | 21 ++-- > chardev/char-mux.c | 1 + > chardev/char-null.c | 1 + > chardev/char-pty.c | 15 ++- > chardev/char-serial.c | 1 + > chardev/char-socket.c | 35 +++++++ > chardev/char-stdio.c | 8 ++ > chardev/char.c | 41 +++++++- > gdbstub.c | 1 + > hmp-commands.hx | 62 ++++++++++++ > hw/core/machine.c | 19 ++++ > hw/pci/msix.c | 20 ++-- > hw/pci/pci.c | 7 +- > hw/vfio/common.c | 78 ++++++++++++-- > hw/vfio/cpr.c | 154 ++++++++++++++++++++++++++++ > hw/vfio/meson.build | 1 + > hw/vfio/pci.c | 230 > +++++++++++++++++++++++++++++++++++++++--- > hw/vfio/trace-events | 1 + > hw/virtio/vhost.c | 11 ++ > include/chardev/char.h | 6 ++ > include/exec/memory.h | 25 +++++ > include/hw/boards.h | 1 + > include/hw/pci/msix.h | 5 + > include/hw/pci/pci.h | 2 + > include/hw/vfio/vfio-common.h | 8 ++ > include/hw/virtio/vhost.h | 1 + > include/migration/cpr.h | 20 ++++ > include/monitor/hmp.h | 4 + > include/qemu/env.h | 23 +++++ > include/qemu/osdep.h | 1 + > include/sysemu/runstate.h | 2 + > include/sysemu/sysemu.h | 1 + > linux-headers/linux/vfio.h | 27 +++++ > migration/cpr.c | 195 +++++++++++++++++++++++++++++++++++ > migration/meson.build | 1 + > migration/migration.c | 5 + > migration/savevm.c | 21 ++-- > migration/savevm.h | 2 + > monitor/hmp-cmds.c | 75 ++++++++++++-- > monitor/hmp.c | 3 + > monitor/qmp-cmds.c | 36 +++++++ > monitor/qmp.c | 3 + > qapi/char.json | 5 +- > qapi/cpr.json | 88 ++++++++++++++++ > qapi/meson.build | 1 + > qapi/qapi-schema.json | 1 + > qemu-options.hx | 39 ++++++- > softmmu/globals.c | 1 + > softmmu/memory.c | 48 +++++++++ > softmmu/physmem.c | 49 +++++++-- > softmmu/runstate.c | 58 ++++++++++- > softmmu/vl.c | 14 ++- > stubs/cpr.c | 3 + > stubs/meson.build | 1 + > trace-events | 1 + > util/env.c | 95 +++++++++++++++++ > util/meson.build | 1 + > util/oslib-posix.c | 9 ++ > util/oslib-win32.c | 4 + > util/qemu-config.c | 4 + > 61 files changed, 1525 insertions(+), 83 deletions(-) > create mode 100644 hw/vfio/cpr.c > create mode 100644 include/migration/cpr.h > create mode 100644 include/qemu/env.h > create mode 100644 migration/cpr.c > create mode 100644 qapi/cpr.json > create mode 100644 stubs/cpr.c > create mode 100644 util/env.c > > -- > 1.8.3.1 > > > It doesn't apply on master, could you rebase and resend? thanks -- Marc-André Lureau
