Live snapshots not working

[dcdelia]

Hello! I built your code with --enable-vmi on Ubuntu 18.04 64-bit and I see a few DLLs successfully scanned for exports when booting Windows 7 SP1 32-bit, so VMI seems to be working. It appears however that snapshots of the running guest do not work properly.

I run my VM with the following options:

i386-softmmu/qemu-system-i386 -m 2048 -monitor stdio -usb -device usb-tablet -netdev user,id=mynet -device rtl8139,netdev=mynet -vnc 127.0.0.1:0 images/win7sp1_x86.qcow2

I tried also changing the disk caching policy to unsafe and disabling the USB tablet pointer with no effect. So when I try to capture a snapshot with savevm mysnap and then load it later with command-line option -loadvm mysnap the display is eventually restored correctly (and some VMI info on libraries is displayed) but the machine is left unresponsive. Checking with info cpus I can see the instruction pointer changing, so perhaps it's not totally frozen but I have no clue of what is going on.

To rule out QEMU known problems, I downloaded the tarball for version 1.0.0 that apparently you use in DECAF and compiled it with --target-list=i386-softmmu --disable-docs --disable-kvm --disable-libiscsi --disable-xen (basically I disabled all the components that led to compilation failures on my machine; I also added LIBS+=-lrt to Makefile.target to get around a linking error). Snapshots can be saved and restored correctly for the same image within vanilla QEMU. I tried restoring a QEMU snapshot into DECAF with no luck (guest still unresponsive), while for the other way around QEMU legitimately complains about the DECAF section:

(qemu) Unknown savevm section or instance 'DECAF' 0
qemu-system-i386: Error -22 while loading VM state