Re: [Qemu-devel] [PATCH 00/15] Make migration work with hotplug

[Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>]

2010/6/24 Alex Williamson <alex.williamson@redhat.com>:
> Ok, new approach.  I'm going to attempt to extract myself for the
> canonical device path approach, because we're missing too many pieces
> to make that work.  Instead, I'll take Anthony's advice and try to
> simplify.  We still want a unique name for ramblocks and savevm, but
> the hotplug problem today is only for PCI devices.  PCI conveniently
> has globally unique, dare I say canonical, addressing in the form of
> <domain>:<bus>:<device>.<func>.  To get to this, let's add a new
> function on the BusInfo structure called get_dev_path().  For a PCI
> device, we can simply traverse up the qdev tree to the BusInfo
> structure, look for the function, and call it to return a global PCI
> address.
>
> For some buses, these functions could chain up to their parent bus
> appending strings together to get a unique path.  An example would be
> USB, where the USB port number may not be unique.  If we traverse up
> to the PCI device providing USB, and then to the PCI bus, we get a
> globally unique PCI path, appended with a USB port number.
>
> To make this work for ramblocks and savevm, we need a DeviceState
> pointer when the they are create/registered, and we need a caller
> provided context in case there are multiple ramblocks/savevm
> associated with a device.  Savevm already provies the context,
> and I've attempted to make reasonable guesses at these for the
> ramblocks.  Note that most of the ramblocks aren't associated with
> a device, so I don't think it makes sense to link savevm and
> ramblocks together with the same absolute id string.
>
> Once we have savevm with unique id strings, rather than hotplug
> unfriendly instance numbers, we can be sure that the right driver
> instance is loading the correct vmstate.  I've also implemented
> a compat field for this, so we can still accept incoming migrations
> from previous versions.
>
> Once we have ramblocks with a unique id string, we can switch to
> using id + offset for migration, which enables a ram_addr_t space
> that supports gaps, which enables us to implement qemu_ram_free().
> With that, I think we can finally do migrations reliable after
> hotplug!  Note that the target VM still needs to be created to
> match the current devices and bus addresses of the source VM.  We
> can also still maintain compatibility for migrations here by bumping
> the ram migration version and supporting both new and old (just
> hope the source hasn't done any hotplugs).
>
> Sound reasonable?  Is get_dev_path the right name?  In the right
> place?  The PCI return is currently "dddd:bb:dd.f", should this be
> "PCI:dddd:bb:dd.f"?  Something else?  Thanks,

Hi Alex,

Is there additional overhead to save rams introduce by this series?
If so, how much?

Thanks,

Yoshi

>
> Alex
>
> ---
>
> Alex Williamson (15):
>      ramblocks: No more being lazy about duplicate names
>      pci: Free the space allocated for the option rom on removal
>      qemu_ram_free: Implement it
>      savevm: Create a new continue flag to avoid resending block name
>      savevm: Use RAM blocks for basis of migration
>      savevm: Migrate RAM based on name/offset
>      ramblocks: Make use of DeviceState pointer and BusInfo.get_dev_path
>      qemu_ram_alloc: Add DeviceState and name parameters
>      virtio-net: Incorporate a DeviceState pointer and let savevm track instances
>      eepro100: Add a dev field to eeprom new/free functions
>      savevm: Make use of DeviceState
>      savevm: Add DeviceState param
>      pci: Implement BusInfo.get_dev_path()
>      qdev: Add a get_dev_path() function to BusInfo
>      Remove uses of ram.last_offset (aka last_ram_offset)
>
>
>  arch_init.c                   |  183 +++++++++++++++++++++++++++++++++++------
>  audio/audio.c                 |    2
>  block-migration.c             |    4 -
>  cpu-all.h                     |    5 +
>  cpu-common.h                  |    2
>  exec.c                        |   96 +++++++++++++++++++---
>  hw/adb.c                      |    4 -
>  hw/ads7846.c                  |    2
>  hw/an5206.c                   |    4 -
>  hw/arm_gic.c                  |    2
>  hw/arm_timer.c                |    4 -
>  hw/armv7m.c                   |    9 +-
>  hw/armv7m_nvic.c              |    2
>  hw/axis_dev88.c               |    4 -
>  hw/cirrus_vga.c               |    2
>  hw/cuda.c                     |    2
>  hw/dma.c                      |    4 -
>  hw/dummy_m68k.c               |    2
>  hw/eepro100.c                 |    8 +-
>  hw/eeprom93xx.c               |    8 +-
>  hw/eeprom93xx.h               |    4 -
>  hw/etraxfs.c                  |    6 +
>  hw/fw_cfg.c                   |    2
>  hw/g364fb.c                   |    4 -
>  hw/grackle_pci.c              |    4 -
>  hw/gt64xxx.c                  |    3 -
>  hw/gumstix.c                  |    6 +
>  hw/heathrow_pic.c             |    2
>  hw/hw.h                       |   18 ++--
>  hw/i2c.c                      |    2
>  hw/i8254.c                    |    2
>  hw/i8259.c                    |    2
>  hw/ide/cmd646.c               |    2
>  hw/ide/isa.c                  |    2
>  hw/ide/macio.c                |    2
>  hw/ide/microdrive.c           |    2
>  hw/ide/mmio.c                 |    2
>  hw/ide/piix.c                 |    2
>  hw/integratorcp.c             |    4 -
>  hw/m48t59.c                   |    2
>  hw/mac_dbdma.c                |    2
>  hw/mac_nvram.c                |    4 -
>  hw/mainstone.c                |    6 +
>  hw/max111x.c                  |    3 -
>  hw/mcf5208.c                  |    4 -
>  hw/mips_jazz.c                |    4 -
>  hw/mips_malta.c               |    4 -
>  hw/mips_mipssim.c             |    4 -
>  hw/mips_r4k.c                 |    6 +
>  hw/mipsnet.c                  |    4 -
>  hw/mst_fpga.c                 |    3 -
>  hw/musicpal.c                 |   11 ++
>  hw/nand.c                     |    2
>  hw/omap1.c                    |    6 +
>  hw/omap2.c                    |    6 +
>  hw/omap_sx1.c                 |   12 ++-
>  hw/onenand.c                  |    2
>  hw/openpic.c                  |    5 +
>  hw/palm.c                     |    3 -
>  hw/pc.c                       |    8 +-
>  hw/pci.c                      |   34 +++++++-
>  hw/pckbd.c                    |    2
>  hw/petalogix_s3adsp1800_mmu.c |    7 +-
>  hw/piix4.c                    |    2
>  hw/pl011.c                    |    2
>  hw/pl022.c                    |    2
>  hw/pl061.c                    |    2
>  hw/ppc405_boards.c            |   18 ++--
>  hw/ppc405_uc.c                |    2
>  hw/ppc4xx_devs.c              |    4 +
>  hw/ppc4xx_pci.c               |    4 -
>  hw/ppc_newworld.c             |    6 +
>  hw/ppc_oldworld.c             |    6 +
>  hw/ppc_prep.c                 |    4 -
>  hw/ppce500_mpc8544ds.c        |    3 -
>  hw/ppce500_pci.c              |    4 -
>  hw/ps2.c                      |    4 -
>  hw/pxa2xx.c                   |   39 +++++----
>  hw/pxa2xx_dma.c               |    2
>  hw/pxa2xx_gpio.c              |    2
>  hw/pxa2xx_keypad.c            |    2
>  hw/pxa2xx_lcd.c               |    2
>  hw/pxa2xx_mmci.c              |    2
>  hw/pxa2xx_pic.c               |    3 -
>  hw/pxa2xx_timer.c             |    2
>  hw/qdev.c                     |    4 -
>  hw/qdev.h                     |    3 +
>  hw/r2d.c                      |    4 -
>  hw/rc4030.c                   |    2
>  hw/realview.c                 |    6 +
>  hw/s390-virtio.c              |    2
>  hw/serial.c                   |    4 -
>  hw/sm501.c                    |    2
>  hw/spitz.c                    |   11 +-
>  hw/ssd0323.c                  |    3 -
>  hw/ssi-sd.c                   |    2
>  hw/stellaris.c                |   11 +-
>  hw/stellaris_enet.c           |    4 -
>  hw/stellaris_input.c          |    2
>  hw/sun4m.c                    |    8 +-
>  hw/sun4u.c                    |    4 -
>  hw/syborg.c                   |    2
>  hw/syborg_fb.c                |    2
>  hw/syborg_interrupt.c         |    3 -
>  hw/syborg_keyboard.c          |    2
>  hw/syborg_pointer.c           |    2
>  hw/syborg_rtc.c               |    3 -
>  hw/syborg_serial.c            |    2
>  hw/syborg_timer.c             |    2
>  hw/tc6393xb.c                 |    2
>  hw/tcx.c                      |    2
>  hw/tosa.c                     |    2
>  hw/tsc2005.c                  |    2
>  hw/tsc210x.c                  |    4 -
>  hw/unin_pci.c                 |    6 +
>  hw/versatilepb.c              |    2
>  hw/vga-isa-mm.c               |    2
>  hw/vga-isa.c                  |    2
>  hw/vga.c                      |    2
>  hw/virtio-balloon.c           |    3 -
>  hw/virtio-blk.c               |    2
>  hw/virtio-net.c               |    7 +-
>  hw/virtio-serial-bus.c        |    2
>  hw/vmmouse.c                  |    2
>  hw/vmware_vga.c               |    4 -
>  hw/zaurus.c                   |    2
>  qemu-timer.c                  |    2
>  savevm.c                      |  106 +++++++++++++++++++++---
>  slirp/slirp.c                 |    5 +
>  vl.c                          |    2
>  130 files changed, 648 insertions(+), 286 deletions(-)
>
>
>