[Xen-users] help please - running a guest from an iSCSI disk ? getting more diagnostics than "cannot make domain: -3" ? how to make domain0 "privileged" ?

[Jason Vas Dias <jason.vas.dias@xxxxxxxxx>]

Good day -

This is my first post to this list , and I'm new to Xen - any help on
this issue would be much appreciated .

I downloaded, built and installed xen-4.2.1 (hypervisor and tools) on
an x86_64 ArchLinux box
updated to latest software as of today.

I am trying to bring up a Linux guest from a remote iSCSI disk.

The iSCSI-initiator (open-iscsi)  logs in to the remote target OK and
makes it available as /dev/sde ,
on which is a bootable linux distribution . containing /boot/vmlinuz* etc.
I can mount this iSCSI disk rw OK on the domain_0 host - so presumably
I should be able to
boot up a guest domain from it ?

I modified the domain_0 host's boot arguments to boot Xen OK :

        multiboot /boot/xen.gz dom0_mem=1024M loglvl=all guest_loglvl=all
        module  /boot/vmlinuz-linux root=/dev/sda2 ro  debug
        module  /boot/initramfs-linux.img

and made an /etc/xen/${domain}.cfg file:
#
# xl.cfg(1) file for booting the iSCSI share:
#
name="$domain"
#vcpus=1
#uuid="ceb083a2-feaa-45b0-afe2-3bd44eb4d8c3"
memory=1024
on_poweroff="destroy"
on_reboot="destroy"
disk=["/dev/sde,raw,hda,rw"]
vif=["mac=00:09:3d:13:0d:57,model=tg3,bridge=xenbr0"]
kernel="/boot/vmlinuz-2.6.39-300.26.1.el6uek.x86_64"
ramdisk="/boot/initramfs-2.6.39-300.26.1.el6uek.x86_64.img"

Is the disk line OK ?  Anything else wrong with this file ?

But attempting to create the domain , as root, fails:
# xl -vvv create -c /etc/xen/${domain}.cfg
Parsing config from ${domain}.cfg
libxl: debug: libxl_create.c:1174:do_domain_create: ao 0x119c890:
create: how=(nil) callback=(nil) poller=0x119c920
libxl: error: libxl_create.c:420:libxl__domain_make: domain creation fail
libxl: error: libxl_create.c:646:initiate_domain_create: cannot make domain: -3
libxl: error: libxl.c:1394:libxl__destroy_domid: non-existant domain -1
libxl: error: libxl.c:1358:domain_destroy_callback: unable to destroy
guest with domid 4294967295
libxl: error: libxl_create.c:1153:domcreate_destruction_cb: unable to
destroy domain 4294967295 following failed creation
libxl: debug: libxl_event.c:1499:libxl__ao_complete: ao 0x119c890:
complete, rc=-3
libxl: debug: libxl_create.c:1187:do_domain_create: ao 0x119c890:
inprogress: poller=0x119c920, flags=ic
libxl: debug: libxl_event.c:1471:libxl__ao__destroy: ao 0x119c890: destroy
xc: debug: hypercall buffer: total allocations:5 total releases:5
xc: debug: hypercall buffer: current allocations:0 maximum allocations:2
xc: debug: hypercall buffer: cache current size:2
xc: debug: hypercall buffer: cache hits:3 misses:2 toobig:0

Even though I've enabled all possible log messages in Xen with '
loglvl=all guest_loglvl=all' (or have I?)
I don't see any log messages about this failed attempt to create a
domain at all , in dmesg output or
in the system log.

Tracing this command in gdb shows the hypervisor command is returning
-1, with errno set to 1 (EPERM) :

libxl: debug: libxl_create.c:1174:do_domain_create: ao 0x622890:
create: how=(nil) callback=(nil) poller=0x622920

Breakpoint 2, xc_domain_create (xch=0x622240, ssidref=0,
handle=handle@entry=0x7fffffffe1b0
"\316\260\203\242\376\252E\260\257\342;\324N\264\330\303\031",
    flags=flags@entry=0, pdomid=pdomid@entry=0x7fffffffe28c) at xc_domain.c:33
33      {
(gdb) n
37          domctl.cmd = XEN_DOMCTL_createdomain;
(gdb)
38          domctl.domain = (domid_t)*pdomid;
(gdb)
39          domctl.u.createdomain.ssidref = ssidref;
(gdb)
40          domctl.u.createdomain.flags   = flags;
(gdb)
41          memcpy(domctl.u.createdomain.handle, handle,
sizeof(xen_domain_handle_t));
(gdb)
42          if ( (err = do_domctl(xch, &domctl)) != 0 )
(gdb) s
do_domctl (domctl=0x7fffffffe0a0, xch=0x622240) at xc_private.h:239
239         DECLARE_HYPERCALL_BOUNCE(domctl, sizeof(*domctl),
XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
(gdb) n
241         domctl->interface_version = XEN_DOMCTL_INTERFACE_VERSION;
(gdb)
243         if ( xc_hypercall_bounce_pre(xch, domctl) )
(gdb)
249         hypercall.op     = __HYPERVISOR_domctl;
(gdb)
250         hypercall.arg[0] = HYPERCALL_BUFFER_AS_ARG(domctl);
(gdb)
252         if ( (ret = do_xen_hypercall(xch, &hypercall)) < 0 )
(gdb) s
do_xen_hypercall (xch=xch@entry=0x622240,
hypercall=hypercall@entry=0x7fffffffe070) at xc_private.c:246
246         return xch->ops->u.privcmd.hypercall(xch, xch->ops_handle,
hypercall);
(gdb) s
linux_privcmd_hypercall (xch=<optimized out>, h=9,
hypercall=0x7fffffffe070) at xc_linux_osdep.c:116
116         return ioctl(fd, IOCTL_PRIVCMD_HYPERCALL, hypercall);
(gdb) fin
Run till exit from #0  linux_privcmd_hypercall (xch=<optimized out>,
h=9, hypercall=0x7fffffffe070) at xc_linux_osdep.c:116
do_xen_hypercall (xch=xch@entry=0x622240,
hypercall=hypercall@entry=0x7fffffffe070) at xc_private.c:247
247     }
Value returned is $3 = -1
(gdb) fin
Run till exit from #0  do_xen_hypercall (xch=xch@entry=0x622240,
hypercall=hypercall@entry=0x7fffffffe070) at xc_private.c:247
0x00007ffff775b340 in do_domctl (domctl=0x7fffffffe0a0, xch=0x622240)
at xc_private.h:252
252         if ( (ret = do_xen_hypercall(xch, &hypercall)) < 0 )
Value returned is $4 = -1
(gdb) p errno
$5 = 1

Any ideas how to get this working,  or on where I could get better
diagnostics ?

I'm guessing this is caused by this code in  arch/x86/platform_hypercall.c :

ret_t do_platform_op(XEN_GUEST_HANDLE(xen_platform_op_t) u_xenpf_op)
{
    ret_t ret = 0;
    struct xen_platform_op curop, *op = &curop;

    if ( !IS_PRIV(current->domain) )
        return -EPERM;

So how do I make the IS_PRIV macro return non-zero for my domain_0 ,
ie. set d->is_privileged /
make my domain0 into a "privileged" domain ? What is meant by
"privileged" in this context ?

There seems to be no documentation on this issue in any manual page
installed by xen's 'make install' ,
or anywhere else I could find.

Thanks in advance for any replies,
Regards, Jason

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