[Xen-devel] ctxt->pt_base != 0 when creating a new domain

[Felipe Alfaro Solana <felipe.alfaro@xxxxxxxxx>]

Hi!

Since upgrading to the latest bkbits from xeno-unstable, I'm unable to
create a XenU domain I was previously able to create with no problems
at all:

# xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      414    0  r----     23.4        

# xm create xenU
Using config file "xenU"
Error: Error creating domain: (0, 'Error')

# cat /var/log/xend-debug.log
network start bridge=xen-br0 netdev=eth1 antispoof=no
ERROR: Domain is already constructed
op_create> Exception creating domain:
Traceback (most recent call last):
  File "/usr/lib/python/xen/xend/server/SrvDomainDir.py", line 66, in op_create
    deferred = self.xd.domain_create(config)
  File "/usr/lib/python/xen/xend/XendDomain.py", line 357, in domain_create
    deferred = XendDomainInfo.vm_create(config)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 195, in vm_create
    ptr = vm.construct(config)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 469, in construct
    self.construct_image()
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 503, in
construct_image
    self.image_handler(self, image)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 1137, in
vm_image_linux
    vm.create_domain("linux", kernel, ramdisk, cmdline)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 809, in create_domain
    self.build_domain(ostype, kernel, ramdisk, cmdline, memmap)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 789, in build_domain
    vcpus          = self.vcpus)
error: (0, 'Error')

I have made the following testcase patch:

--- tools/libxc/xc_linux_build.c.old    2005-02-07 13:49:57.000000000 +0100
+++ tools/libxc/xc_linux_build.c        2005-02-07 14:45:35.242555000 +0100
@@ -360,46 +360,51 @@
             goto error_out;
         }
     }
 
     if ( mlock(&st_ctxt, sizeof(st_ctxt) ) )
     {   
         PERROR("Unable to mlock ctxt");
         return 1;
     }
 
     op.cmd = DOM0_GETDOMAININFO;
     op.u.getdomaininfo.domain = (domid_t)domid;
     op.u.getdomaininfo.exec_domain = 0;
     op.u.getdomaininfo.ctxt = ctxt;
     if ( (do_dom0_op(xc_handle, &op) < 0) || 
          ((u16)op.u.getdomaininfo.domain != domid) )
     {
         PERROR("Could not get info on domain");
         goto error_out;
     }
+#if 1
     if ( !(op.u.getdomaininfo.flags & DOMFLAGS_PAUSED) ||
          (ctxt->pt_base != 0) )
     {
-               ERROR("Domain is already constructed");
+       if (!(op.u.getdomaininfo.flags & DOMFLAGS_PAUSED))
+               ERROR("Cannot create an unpaused domain");
+       else
+               ERROR("Domain is already constructed or ctxt->pt_base != 0");
         goto error_out;
     }
+#endif
 
     if ( setup_guestos(xc_handle, domid, image, image_size, 
                        initrd_gfd, initrd_size, nr_pages, 
                        &vstartinfo_start, &vkern_entry,
                        ctxt, cmdline,
                        op.u.getdomaininfo.shared_info_frame,
                        control_evtchn, flags, vcpus) < 0 )
     {
         ERROR("Error constructing guest OS");
         goto error_out;
     }
 
     if ( initrd_fd >= 0 )
         close(initrd_fd);
     if ( initrd_gfd )
         gzclose(initrd_gfd);
     if ( image != NULL )
         free(image);
 
     ctxt->flags = 0;


After applying the previous patch, rebuilnding and rebooting, this is
what gets logged into xend-debug.log:

# cat /var/log/xend-debug.log
network start bridge=xen-br0 netdev=eth1 antispoof=no
ERROR: Domain is already constructed or ctxt->pt_base != 0
op_create> Exception creating domain:
Traceback (most recent call last):
  File "/usr/lib/python/xen/xend/server/SrvDomainDir.py", line 66, in op_create
    deferred = self.xd.domain_create(config)
  File "/usr/lib/python/xen/xend/XendDomain.py", line 357, in domain_create
    deferred = XendDomainInfo.vm_create(config)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 195, in vm_create
    ptr = vm.construct(config)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 469, in construct
    self.construct_image()
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 503, in
construct_image
    self.image_handler(self, image)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 1137, in
vm_image_linux
    vm.create_domain("linux", kernel, ramdisk, cmdline)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 809, in create_domain
    self.build_domain(ostype, kernel, ramdisk, cmdline, memmap)
  File "/usr/lib/python/xen/xend/XendDomainInfo.py", line 789, in build_domain
    vcpus          = self.vcpus)
error: (0, 'Error')

This reveals that, for some misterious reason, the condition
"ctxt->pt_base != 0" evaluates TRUE. Why is this happening? What's
more, replacing the "#if 1" with an "#if 0" fixes the problem for me:
the domain is created and works properly.

Any ideas?


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