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Re: [PATCH V6 00/27] Live Update
From: |
Steven Sistare |
Subject: |
Re: [PATCH V6 00/27] Live Update |
Date: |
Mon, 9 Aug 2021 12:02:07 -0400 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 |
I forgot to mention in the changes list: I added a new mechanism to save fd
values,
in lieu of the environment. See [PATCH V6 13/27] cpr: preserve extra state
- Steve
On 8/6/2021 5:43 PM, Steve Sistare wrote:
> Provide the cpr-save, cpr-exec, and cpr-load 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.
>
> cpr-save 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 cpr-save and cpr-load. It supports two modes:
> reboot and restart.
>
> In reboot mode, the caller invokes cpr-save 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 cpr-load. 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.yznaga@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 cpr-save, the caller passes qemu command-line arguments to cpr-exec,
> 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 cpr-load 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.sistare@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 cpr-load, which loads state from
> the file. If the VM was running at cpr-save time, then VM execution resumes.
> If the VM was suspended at cpr-save time (reboot mode), then the caller must
> issue a system_wakeup command to resume.
>
> The first patches add reboot mode:
> - memory: qemu_check_ram_volatile
> - migration: fix populate_vfio_info
> - migration: qemu file wrappers
> - migration: simplify savevm
> - vl: start on wakeup request
> - cpr: reboot mode
> - cpr: reboot HMP interfaces
>
> The next patches add restart mode:
> - memory: flat section iterator
> - oslib: qemu_clear_cloexec
> - machine: memfd-alloc option
> - qapi: list utility functions
> - vl: helper to request re-exec
> - cpr: preserve extra state
> - cpr: restart mode
> - cpr: restart HMP interfaces
> - hostmem-memfd: cpr for memory-backend-memfd
>
> The next patches add vfio support for restart mode:
> - pci: export functions for cpr
> - vfio-pci: refactor for cpr
> - vfio-pci: cpr part 1 (fd and dma)
> - vfio-pci: cpr part 2 (msi)
> - vfio-pci: cpr part 3 (intx)
>
> The next patches preserve various descriptor-based backend devices across
> cprexec:
> - vhost: reset vhost devices for cpr
> - chardev: cpr framework
> - chardev: cpr for simple devices
> - chardev: cpr for pty
> - chardev: cpr for sockets
> - cpr: only-cpr-capable option
>
> 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) cpr-save /tmp/qemu.sav restart |
> (qemu) cpr-exec qemu-system-x86_64 -S ... |
> QEMU 4.2.1 monitor - type 'help' ... |
> (qemu) info status |
> VM status: paused (prelaunch) |
> (qemu) cpr-load /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) cpr-save /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) cpr-load /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
>
> Changes from V4 to V5:
> - rebase to master
>
> Changes from V5 to V6:
> vfio:
> - delete redundant bus_master_enable_region in vfio_pci_post_load
> - delete unmap.size warning
> - fix phys_config memory leak
> - add INTX support
> - add vfio_named_notifier_init() helper
> Other:
> - 6.1 -> 6.2
> - rename file -> filename in qapi
> - delete cprinfo. qapi introspection serves the same purpose.
> - rename cprsave, cprexec, cprload -> cpr-save, cpr-exec, cpr-load
> - improve documentation in qapi/cpr.json
> - rename qemu_ram_volatile -> qemu_ram_check_volatile, and use
> qemu_ram_foreach_block
> - rename handle -> opaque
> - use ERRP_GUARD
> - use g_autoptr and g_autofree, and glib allocation functions
> - conform to error conventions for bool and int function return values
> and function names.
> - remove word "error" in error messages
> - rename as_flat_walk and its callback, and add comments.
> - rename qemu_clr_cloexec -> qemu_clear_cloexec
> - rename close-on-cpr -> reopen-on-cpr
> - add strList utility functions
> - factor out start on wakeup request to a separate patch
> - deleted unnecessary layer (cprsave etc) and squashed QMP patches
> - conditionally compile for CONFIG_VFIO
>
> Steve Sistare (24):
> memory: qemu_check_ram_volatile
> migration: fix populate_vfio_info
> migration: qemu file wrappers
> migration: simplify savevm
> vl: start on wakeup request
> cpr: reboot mode
> memory: flat section iterator
> oslib: qemu_clear_cloexec
> machine: memfd-alloc option
> qapi: list utility functions
> vl: helper to request re-exec
> cpr: preserve extra state
> cpr: restart mode
> cpr: restart HMP interfaces
> hostmem-memfd: cpr for memory-backend-memfd
> pci: export functions for cpr
> vfio-pci: refactor for cpr
> vfio-pci: cpr part 1 (fd and dma)
> vfio-pci: cpr part 2 (msi)
> vfio-pci: cpr part 3 (intx)
> chardev: cpr framework
> chardev: cpr for simple devices
> chardev: cpr for pty
> cpr: only-cpr-capable option
>
> Mark Kanda, Steve Sistare (3):
> cpr: reboot HMP interfaces
> vhost: reset vhost devices for cpr
> 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 | 14 +-
> chardev/char-serial.c | 1 +
> chardev/char-socket.c | 36 +++++
> chardev/char-stdio.c | 8 ++
> chardev/char.c | 43 +++++-
> gdbstub.c | 1 +
> hmp-commands.hx | 50 +++++++
> hw/core/machine.c | 19 +++
> hw/pci/msix.c | 20 ++-
> hw/pci/pci.c | 7 +-
> hw/vfio/common.c | 79 +++++++++--
> hw/vfio/cpr.c | 160 ++++++++++++++++++++++
> hw/vfio/meson.build | 1 +
> hw/vfio/pci.c | 301
> +++++++++++++++++++++++++++++++++++++++---
> hw/vfio/trace-events | 1 +
> hw/virtio/vhost.c | 11 ++
> include/chardev/char.h | 6 +
> include/exec/memory.h | 39 ++++++
> 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 | 31 +++++
> include/monitor/hmp.h | 3 +
> include/qapi/util.h | 28 ++++
> include/qemu/osdep.h | 1 +
> include/sysemu/runstate.h | 2 +
> include/sysemu/sysemu.h | 1 +
> linux-headers/linux/vfio.h | 6 +
> migration/cpr-state.c | 215 ++++++++++++++++++++++++++++++
> migration/cpr.c | 176 ++++++++++++++++++++++++
> migration/meson.build | 2 +
> migration/migration.c | 5 +
> migration/qemu-file-channel.c | 36 +++++
> migration/qemu-file-channel.h | 6 +
> migration/savevm.c | 21 +--
> migration/target.c | 24 +++-
> migration/trace-events | 5 +
> monitor/hmp-cmds.c | 68 ++++++----
> monitor/hmp.c | 3 +
> monitor/qmp.c | 3 +
> qapi/char.json | 7 +-
> qapi/cpr.json | 76 +++++++++++
> qapi/meson.build | 1 +
> qapi/qapi-schema.json | 1 +
> qapi/qapi-util.c | 37 ++++++
> qemu-options.hx | 40 +++++-
> softmmu/globals.c | 1 +
> softmmu/memory.c | 46 +++++++
> softmmu/physmem.c | 55 ++++++--
> softmmu/runstate.c | 38 +++++-
> softmmu/vl.c | 18 ++-
> stubs/cpr-state.c | 15 +++
> stubs/cpr.c | 3 +
> stubs/meson.build | 2 +
> trace-events | 1 +
> util/oslib-posix.c | 9 ++
> util/oslib-win32.c | 4 +
> util/qemu-config.c | 4 +
> 64 files changed, 1732 insertions(+), 111 deletions(-)
> create mode 100644 hw/vfio/cpr.c
> create mode 100644 include/migration/cpr.h
> create mode 100644 migration/cpr-state.c
> create mode 100644 migration/cpr.c
> create mode 100644 qapi/cpr.json
> create mode 100644 stubs/cpr-state.c
> create mode 100644 stubs/cpr.c
>
- Re: [PATCH V6 19/27] vfio-pci: cpr part 1 (fd and dma), (continued)
- [PATCH V6 22/27] vhost: reset vhost devices for cpr, Steve Sistare, 2021/08/06
- [PATCH V6 23/27] chardev: cpr framework, Steve Sistare, 2021/08/06
- [PATCH V6 25/27] chardev: cpr for pty, Steve Sistare, 2021/08/06
- [PATCH V6 26/27] chardev: cpr for sockets, Steve Sistare, 2021/08/06
- [PATCH V6 27/27] cpr: only-cpr-capable option, Steve Sistare, 2021/08/06
- [PATCH V6 01/27] memory: qemu_check_ram_volatile, Steve Sistare, 2021/08/06
- [PATCH V6 21/27] vfio-pci: cpr part 3 (intx), Steve Sistare, 2021/08/06
- [PATCH V6 24/27] chardev: cpr for simple devices, Steve Sistare, 2021/08/06
- Re: [PATCH V6 00/27] Live Update,
Steven Sistare <=
- Re: [PATCH V6 00/27] Live Update, Zheng Chuan, 2021/08/21