Re: [Xen-users] Xen 4.1 with tmem / xm save -> crash

[Jana Saout <jana@xxxxxxxx>]

Hello again,

> Apparently buf.p (%rcx) is NULL.
> 
> I've been trying to figure out how this could happen, but don't know
> enough about the mechanisms involved to figure it out.  Apparently this
> op gets called from Dom0 userspace (xend, tools/libxc/xc_tmem.c):
> 
> (void)xc_tmem_control(xch,i,TMEMC_SAVE_GET_POOL_UUID,dom,sizeof(uuid),0,0,&uuid);
> 
> Which then calls
> 
> xen_set_guest_handle(op.u.ctrl.buf, buf);
> rc = do_tmem_op(xch,&op);
> 
> There are also calls to some bounce buffer handling in case subop is
> TMEMC_LIST, but not in the other cases. (no clue what this is about)

I just changed to code to not check for TMEMC_LIST only, but to always
call the bounce buffer pre and post code whenever buf is != NULL.

Now, the "xm save" works.

But, the xm restore fails with:
[2012-06-23 12:11:18 7753] DEBUG (XendCheckpoint:305) [xc_restore]: 
/usr/lib/xen-4.1/bin/xc_restore 23 3 1 2 0 0 0 0
[2012-06-23 12:11:18 7753] INFO (XendCheckpoint:423) xc: error: error 
reading/restoring tmem (1 = Operation not permitted): Internal error
[2012-06-23 12:11:18 7753] INFO (XendCheckpoint:423) xc: error: Error when 
reading batch (1 = Operation not permitted): Internal error

and

[2012-06-23 12:11:19 7753] ERROR (XendCheckpoint:357) 
/usr/lib/xen-4.1/bin/xc_restore 23 3 1 2 0 0 0 0 failed

"xm dmesg" says:

(XEN) tmem: initializing tmem capability for domid=3...ok
(XEN) tmem: compression enabled for all domains, cannot be changed when 
tmem_dedup is enabled
(XEN) tmem: weight set to 0 for domid=3
(XEN) tmem: cap set to 0 for domid=3
(XEN) tmem: allocating ephemeral-private tmem pool for domid=3...failed... 
unsupported spec version
(XEN) tmem: flushing tmem pools for domid=3

Can anyone confirm tmem + xm save/restore/migrate is working for him/her
at all when tmem is in use?

Thanks,
        Jana



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