virtconsole migration regression from 2.2.0

I'm hitting an error migrating from stock v2.2.0 to git master:

2015-03-24T21:42:07.731317Z qemu-system-x86_64: error while loading state for
instance 0x0 of device '0000:00:05.0/virtio-console'
2015-03-24T21:42:07.731392Z qemu-system-x86_64: load of migration failed:
Invalid argument

I'm using libvirt's managedsave, which is migrate to/from file. I bisected to
this commit:

commit 9b70c1790acacae54d559d38ca69186a85040bb8
Author: Michael S. Tsirkin <mst@redhat.com>
Date:   Mon Feb 16 22:36:26 2015 +0100

    virtio-serial: switch to standard-headers

Problem seems to be that the old virtio_console_config structure was
different, missing the emerg_wr field. If I apply this patch:

My VMs restore correctly. I assume that change isn't acceptable as-is though...

Here's the massive libvirt command line:

/home/crobinso/src/qemu/x86_64-softmmu/qemu-system-x86_64 -name
migrateion-tester.py-vm -S -machine pc-i440fx-2.2,accel=kvm,usb=off -cpu
Opteron_G4,+nodeid_msr,+wdt,+skinit,+ibs,+osvw,+cr8legacy,+extapic,+cmp_legacy,+fxsr_opt,+mmxext,+osxsave,+monitor,+ht,+vme
-m 2048 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid
ce2a1280-78e5-7233-3f67-139dfedfdfe9 -no-user-config -nodefaults -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/migrateion-tester.py-vm.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
-boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device
virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive
file=/mnt/data/devel/images/ztester-f18-migrate-overlay.qcow2,if=none,id=drive-virtio-disk0,format=qcow2
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
-netdev tap,fd=27,id=hostnet0,vhost=on,vhostfd=28 -device
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:40:ee:0b,bus=pci.0,addr=0x3 -chardev
spicevmc,id=charchannel0,name=vdagent -device
virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0
-chardev pty,id=charconsole0 -device
virtconsole,chardev=charconsole0,id=console0 -device usb-tablet,id=input0
-spice
port=5901,tls-port=5902,addr=127.0.0.1,disable-ticketing,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on
-device
qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vgamem_mb=16,bus=pci.0,addr=0x2
-device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device
hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -incoming fd:24 -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -snapshot -msg timestamp=on


I tried to reduce it to a minimal reproducer but I couldn't trigger it, but I
didn't try too long. I can test any proposed fix though.

Thanks,
Cole

On Tue, Mar 24, 2015 at 06:14:44PM -0400, Cole Robinson wrote:
> I'm hitting an error migrating from stock v2.2.0 to git master:
> 
> 2015-03-24T21:42:07.731317Z qemu-system-x86_64: error while loading state for
> instance 0x0 of device '0000:00:05.0/virtio-console'
> 2015-03-24T21:42:07.731392Z qemu-system-x86_64: load of migration failed:
> Invalid argument
> 
> I'm using libvirt's managedsave, which is migrate to/from file. I bisected to
> this commit:
> 
> commit 9b70c1790acacae54d559d38ca69186a85040bb8
> Author: Michael S. Tsirkin <mst@redhat.com>
> Date:   Mon Feb 16 22:36:26 2015 +0100
> 
>     virtio-serial: switch to standard-headers
> 
> Problem seems to be that the old virtio_console_config structure was
> different, missing the emerg_wr field. If I apply this patch:
> 
> diff --git a/include/standard-headers/linux/virtio_console.h
> b/include/standard-headers/linux/virtio_console.h
> index 0dedc9e..242a0c5 100644
> --- a/include/standard-headers/linux/virtio_console.h
> +++ b/include/standard-headers/linux/virtio_console.h
> @@ -50,8 +50,6 @@ struct virtio_console_config {
>         uint16_t rows;
>         /* max. number of ports this device can hold */
>         uint32_t max_nr_ports;
> -       /* emergency write register */
> -       uint32_t emerg_wr;
>  } QEMU_PACKED;
> 
> 
> My VMs restore correctly. I assume that change isn't acceptable as-is though...

Thanks! I see the problem, will fix it shortly.

> Here's the massive libvirt command line:
> 
> /home/crobinso/src/qemu/x86_64-softmmu/qemu-system-x86_64 -name
> migrateion-tester.py-vm -S -machine pc-i440fx-2.2,accel=kvm,usb=off -cpu
> Opteron_G4,+nodeid_msr,+wdt,+skinit,+ibs,+osvw,+cr8legacy,+extapic,+cmp_legacy,+fxsr_opt,+mmxext,+osxsave,+monitor,+ht,+vme
> -m 2048 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid
> ce2a1280-78e5-7233-3f67-139dfedfdfe9 -no-user-config -nodefaults -chardev
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/migrateion-tester.py-vm.monitor,server,nowait
> -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
> -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device
> virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive
> file=/mnt/data/devel/images/ztester-f18-migrate-overlay.qcow2,if=none,id=drive-virtio-disk0,format=qcow2
> -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
> -netdev tap,fd=27,id=hostnet0,vhost=on,vhostfd=28 -device
> virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:40:ee:0b,bus=pci.0,addr=0x3 -chardev
> spicevmc,id=charchannel0,name=vdagent -device
> virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0
> -chardev pty,id=charconsole0 -device
> virtconsole,chardev=charconsole0,id=console0 -device usb-tablet,id=input0
> -spice
> port=5901,tls-port=5902,addr=127.0.0.1,disable-ticketing,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on
> -device
> qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vgamem_mb=16,bus=pci.0,addr=0x2
> -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device
> hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -incoming fd:24 -device
> virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -snapshot -msg timestamp=on
> 
> 
> I tried to reduce it to a minimal reproducer but I couldn't trigger it, but I
> didn't try too long. I can test any proposed fix though.
> 
> Thanks,
> Cole