Re: [Qemu-devel] Cubietruck: cannot create KVM guests: "kvm_init_vcpu failed: Invalid argument"

[Kashyap Chamarthy]

On Tue, Dec 09, 2014 at 11:27:02AM +0000, Richard W.M. Jones wrote:
> On Tue, Dec 09, 2014 at 10:53:41AM +0000, Peter Maydell wrote:
> > On 9 December 2014 at 10:50, Kashyap Chamarthy <kcham...@redhat.com> wrote:
> > > Booting a minimal KVM guest throws the below error on Cubietruck:
> > >
> > >   "kvm_init_vcpu failed: Invalid argument"

[. . .]

> > >     So that's the answer really, it's a qemu bug.  Actually it looks as
> > >     if qemu contains some code to try to get the host CPU type, but it
> > >     doesn't work, or maybe we need to pass a -cpu option ..."
> > 
> > Yes, you need to pass a -cpu option. For KVM on ARM, you
> > always need to either:
> >  * pass a -cpu option matching the host CPU
> >  * pass "-cpu host"
> > 
> > The CubieTruck is a Cortex-A7, which we don't have specific
> > support for in QEMU, so you will need "-cpu host".
> 
> Kashyap ^^ can you try this?  Should be a trivial one-liner change
> in src/launch-direct.c.

Yes it works with it :-)

With the below diff in `libguestfs`:

    $ git diff src/launch.c
    diff --git a/src/launch.c b/src/launch.c
    index 9fadce8..ce71a8e 100644
    --- a/src/launch.c
    +++ b/src/launch.c
    @@ -400,7 +400,7 @@ const char *
     guestfs___get_cpu_model (int kvm)
     {
     #if defined(__arm__)            /* 32 bit ARM. */
    -  return NULL;
    +  return "host";
     
     #elif defined(__aarch64__)
       /* With -M virt, the default -cpu is cortex-a15.  Stupid. */


I can boot a KVM guest successfully on Cubietruck, invoked via
libguestfs appliance:

. . .
[01433ms] /bin/qemu-system-arm \
    -global virtio-blk-device.scsi=off \
    -nodefconfig \
    -enable-fips \
    -nodefaults \
    -display none \
    -M vexpress-a15 \
    -cpu host \
    -machine accel=kvm:tcg \
    -m 500 \
    -no-reboot \
    -rtc driftfix=slew \
    -global kvm-pit.lost_tick_policy=discard \
    -kernel /home/kashyapc/src/libguestfs/tmp/.guestfs-1000/appliance.d/kernel \
    -dtb /home/kashyapc/src/libguestfs/tmp/.guestfs-1000/appliance.d/dtb \
    -initrd /home/kashyapc/src/libguestfs/tmp/.guestfs-1000/appliance.d/initrd \
    -device virtio-scsi-device,id=scsi \
    -drive 
file=/home/kashyapc/src/libguestfs/tmp/libguestfsRMfHzO/scratch.1,cache=unsafe,format=raw,id=hd0,if=none
 \
    -device scsi-hd,drive=hd0 \
    -drive 
file=/home/kashyapc/src/libguestfs/tmp/.guestfs-1000/appliance.d/root,snapshot=on,id=appliance,cache=unsafe,if=none
 \
    -device scsi-hd,drive=appliance \
    -device virtio-serial-device \
    -serial stdio \
    -chardev 
socket,path=/home/kashyapc/src/libguestfs/tmp/libguestfsRMfHzO/guestfsd.sock,id=channel0
 \
    -device virtserialport,chardev=channel0,name=org.libguestfs.channel.0 \
    -append 'panic=1 mem=500M console=ttyAMA0 udevtimeout=6000 
udev.event-timeout=6000 no_timer_check acpi=off printk.time=1 
cgroup_disable=memory root=/dev/sdb selinux=0 guestfs_verbose=1 TERM=vt102'
. . .


Thanks, Rich & Peter.

-- 
/kashyap