Re: [PATCH 0/6] Save state error handling (kill off no_migrate)

Michael S. Tsirkin
2010-11-08T11:40:52Z

On Wed, Oct 06, 2010 at 02:58:57PM -0600, Alex Williamson wrote:
> Our code paths for saving or migrating a VM are full of functions that
> return void, leaving no opportunity for a device to cancel a migration,
> either from error or incompatibility. The ivshmem driver attempted to
> solve this with a no_migrate flag on the save state entry. I think the
> more generic and flexible way to solve this is to allow driver save
> functions to fail. This series implements that and converts ivshmem
> to uses a set_params function to NAK migration much earlier in the
> processes. This touches a lot of files, but bulk of those changes are
> simply s/void/int/ and tacking a "return 0" to the end of functions.
> Thanks,
>
> Alex

Well error handling is always tricky: it seems easier to
require save handlers to never fail.
So there's a bunch of code here but what exactly is the benefit?
Since save handlers have no idea what does the remote do,
what is the compatibility you mention?

> ---
>
> Alex Williamson (6):
> savevm: Remove register_device_unmigratable()
> savevm: Allow set_params and save_live_state to error
> virtio: Allow virtio_save() errors
> pci: Allow pci_device_save() to return error
> savevm: Allow vmsd->pre_save to return error
> savevm: Allow SaveStateHandler() to return error
>
>
> block-migration.c | 4 +-
> hw/adb.c | 8 +++-
> hw/ads7846.c | 4 +-
> hw/arm_gic.c | 4 +-
> hw/arm_timer.c | 6 ++-
> hw/armv7m_nvic.c | 4 +-
> hw/cuda.c | 4 +-
> hw/fdc.c | 3 +
> hw/g364fb.c | 4 +-
> hw/grackle_pci.c | 4 +-
> hw/gt64xxx.c | 4 +-
> hw/heathrow_pic.c | 4 +-
> hw/hpet.c | 3 +
> hw/hw.h | 12 ++----
> hw/i2c.c | 3 +
> hw/ide/core.c | 4 +-
> hw/ivshmem.c | 30 +++++++++++----
> hw/lsi53c895a.c | 4 +-
> hw/m48t59.c | 4 +-
> hw/mac_dbdma.c | 4 +-
> hw/mac_nvram.c | 4 +-
> hw/max111x.c | 4 +-
> hw/mipsnet.c | 4 +-
> hw/mst_fpga.c | 3 +
> hw/nand.c | 3 +
> hw/openpic.c | 4 +-
> hw/pci.c | 9 +++-
> hw/pci.h | 2 -
> hw/piix4.c | 4 +-
> hw/pl011.c | 4 +-
> hw/pl022.c | 4 +-
> hw/pl061.c | 4 +-
> hw/ppc4xx_pci.c | 11 ++++-
> hw/ppce500_pci.c | 11 ++++-
> hw/pxa2xx.c | 28 ++++++++++----
> hw/pxa2xx_dma.c | 4 +-
> hw/pxa2xx_gpio.c | 4 +-
> hw/pxa2xx_keypad.c | 3 +
> hw/pxa2xx_lcd.c | 4 +-
> hw/pxa2xx_mmci.c | 4 +-
> hw/pxa2xx_pic.c | 4 +-
> hw/pxa2xx_timer.c | 4 +-
> hw/rc4030.c | 4 +-
> hw/rtl8139.c | 4 +-
> hw/serial.c | 3 +
> hw/spitz.c | 14 +++++--
> hw/ssd0323.c | 4 +-
> hw/ssi-sd.c | 4 +-
> hw/stellaris.c | 20 +++++++---
> hw/stellaris_enet.c | 4 +-
> hw/stellaris_input.c | 4 +-
> hw/syborg_fb.c | 4 +-
> hw/syborg_interrupt.c | 3 +
> hw/syborg_keyboard.c | 3 +
> hw/syborg_pointer.c | 3 +
> hw/syborg_rtc.c | 4 +-
> hw/syborg_serial.c | 4 +-
> hw/syborg_timer.c | 4 +-
> hw/tsc2005.c | 4 +-
> hw/tsc210x.c | 4 +-
> hw/twl92230.c | 3 +
> hw/unin_pci.c | 4 +-
> hw/usb-uhci.c | 3 +
> hw/virtio-balloon.c | 9 +++-
> hw/virtio-blk.c | 10 ++++-
> hw/virtio-net.c | 11 ++++-
> hw/virtio-pci.c | 10 ++++-
> hw/virtio-serial-bus.c | 10 ++++-
> hw/virtio.c | 14 +++++--
> hw/virtio.h | 4 +-
> hw/wm8750.c | 3 +
> hw/zaurus.c | 4 +-
> qemu-common.h | 2 -
> savevm.c | 88 +++++++++++++++++++------------------------
> slirp/slirp.c | 6 ++-
> target-arm/machine.c | 3 +
> target-cris/machine.c | 3 +
> target-i386/machine.c | 7 ++-
> target-microblaze/machine.c | 3 +
> target-mips/machine.c | 3 +
> target-ppc/machine.c | 3 +
> target-s390x/machine.c | 3 +
> target-sparc/machine.c | 3 +
> 83 files changed, 365 insertions(+), 181 deletions(-)
> --
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