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

[Richard W.M. Jones]

On Tue, Dec 09, 2014 at 05:48:04PM +0100, Kashyap Chamarthy wrote:
> 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 <kchamart at 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'
> . . .

Kashyap, how about the following patch as discussed on IRC ...

Rich.

-- 
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-------------- next part --------------
>From 6468b9d60172bcef76b36c14b72f9a1913d94954 Mon Sep 17 00:00:00 2001
From: Kashyap Chamarthy <kchamart at redhat.com>
Date: Tue, 9 Dec 2014 16:58:11 +0000
Subject: [PATCH] arm: Use -cpu host on KVM.

---
 src/launch.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/launch.c b/src/launch.c
index 9fadce8..78d26fe 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -400,7 +400,10 @@ const char *
 guestfs___get_cpu_model (int kvm)
 {
 #if defined(__arm__)            /* 32 bit ARM. */
-  return NULL;
+  if (kvm)
+    return "host";
+  else
+    return NULL;
 
 #elif defined(__aarch64__)
   /* With -M virt, the default -cpu is cortex-a15.  Stupid. */
-- 
2.1.0