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Subject: Re: [Qemu-devel] 2.0 regression: loadvm assertion with ehci + tablet
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To: Cole Robinson <crobinso@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>

Hi,

Am 30.03.2014 22:27, schrieb Cole Robinson:
> With git master, loadvm hits an assert failure if using ehci and usb ta=
blet.
> Steps to reproduce:
>=20
> $ qemu-img create -f qcow2 foo.qcow2 10G
> $ ./x86_64-softmmu/qemu-system-x86_64 \
>   -enable-kvm -m 4096 \
>   -device ich9-usb-ehci1,id=3Dusb,bus=3Dpci.0,addr=3D0x5.0x7 \
>   -device
> ich9-usb-uhci1,masterbus=3Dusb.0,firstport=3D0,bus=3Dpci.0,multifunctio=
n=3Don,addr=3D0x5 \
>   -device ich9-usb-uhci2,masterbus=3Dusb.0,firstport=3D2,bus=3Dpci.0,ad=
dr=3D0x5.0x1 \
>   -device ich9-usb-uhci3,masterbus=3Dusb.0,firstport=3D4,bus=3Dpci.0,ad=
dr=3D0x5.0x2 \
>   -device usb-tablet,id=3Dinput0 \
>   -hda foo.qcow2 \
>   -cdrom Fedora-20-x86_64-Live-Desktop.iso \
>   -boot d -monitor stdio
>=20
> <wait until guest boot to 'welcome to fedora' window>
> (qemu) savevm foo
> (qemu) loadvm foo
> qemu-system-x86_64: hw/pci/pci.c:250: pcibus_reset: Assertion
> `bus->irq_count[i] =3D=3D 0' failed.
>=20
> The relevant backtrace bits for the assertion:
>=20
> #4  0x00007f8f7241971e in pcibus_reset (qbus=3D0x7f8f74082fd0)
>     at hw/pci/pci.c:250
> #5  0x00007f8f723bd36d in qbus_reset_one (bus=3D0x7f8f74082fd0,
>     opaque=3D<optimized out>) at hw/core/qdev.c:249
> #6  0x00007f8f723bec88 in qdev_walk_children (dev=3D0x7f8f73efb320,
>     pre_devfn=3D0x0, pre_busfn=3D0x0, post_devfn=3D0x7f8f723bf4f0 <qdev=
_reset_one>,
>     post_busfn=3D0x7f8f723bd320 <qbus_reset_one>, opaque=3D0x0)
>     at hw/core/qdev.c:403
> #7  0x00007f8f723bedb8 in qbus_walk_children (bus=3D0x7f8f740706e0,
>     pre_devfn=3D0x0, pre_busfn=3D0x0, post_devfn=3D0x7f8f723bf4f0 <qdev=
_reset_one>,
>     post_busfn=3D0x7f8f723bd320 <qbus_reset_one>, opaque=3D0x0)
>     at hw/core/qdev.c:369
> #8  0x00007f8f724f5c5d in qemu_devices_reset () at vl.c:1867
> #9  qemu_system_reset (report=3Dreport@entry=3Dfalse) at vl.c:1880
> #10 0x00007f8f7256dba2 in load_vmstate (name=3Dname@entry=3D0x7f8f7417a=
160 "foo")
>     at /home/crobinso/src/qemu/savevm.c:1098
>=20
> The 'cause' is this:
>=20
> #0  ehci_detach (port=3D0x555556436968) at hw/usb/hcd-ehci.c:810
> #1  0x0000555555727b5e in usb_detach (port=3Dport@entry=3D0x55555643696=
8)
>     at hw/usb/core.c:49
> #2  0x0000555555736bf3 in ehci_reset (opaque=3D0x5555564364d8)
>     at hw/usb/hcd-ehci.c:941
> #3  0x00005555557e1fcd in qemu_devices_reset () at vl.c:1867
> #4  qemu_system_reset (report=3Dreport@entry=3Dfalse) at vl.c:1880
> #5  0x0000555555859f12 in load_vmstate (name=3Dname@entry=3D0x555556458=
210 "foo")
>     at /home/crobinso/src/qemu/savevm.c:1098
>=20
> ehci_reset calls usb_detach which sets pcibus->irq_count[3] =3D 1. pcib=
us_reset
> runs and hits the assertion. But I don't understand this stuff enough t=
o
> determine what's actually wrong here :)
>=20
> I bisected the issue to:
>=20
> commit 31b030d4abc5bea89c2b33b39d3b302836f6b6ee
> Author: Andreas F=C3=A4rber <afaerber@suse.de>
> Date:   Wed Sep 4 01:29:02 2013 +0200
>=20
>     cputlb: Change tlb_flush_page() argument to CPUState
>=20
>     Signed-off-by: Andreas F=C3=A4rber <afaerber@suse.de>
>=20
> ...and then I double checked it since that sounds unrelated. Same resul=
t.

You are running into an unrelated migration bug:
http://git.qemu.org/?p=3Dqemu.git;a=3Dcommit;h=3Dc01a71c1a56fa27f43449ff5=
9e5d03b2483658a2

Sorry about that. You'll need to patch -p1 the above commit on top of
each git-bisect commit to find the actual breakage if the above commit
is already bad (can't test right now).

Cheers,
Andreas

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