[Xen-devel] expandable grant table bug?

["Kasai Takanori" <kasai.takanori@xxxxxxxxxxxxxx>]

Hi All,

Grant table had been expanded before.
As a result, it is thought that it came to be able to use four VNIF or more.

The PV domain operated without trouble.
However, VNIF can be only used up to three in DomVTx(x86).

# xm network-attach 27
# xm network-attach 27
# xm network-attach 27
# xm network-attach 27
# xm network-list 27
Idx BE     MAC Addr.     handle state evt-ch tx-/rx-ring-ref BE-path
0   0  02:17:42:2f:01:11    0     4      5     1280 /1281 
/local/domain/0/backend/vif/27/0
1   0  02:17:42:2f:03:11    1     4      6     1282 /1283 
/local/domain/0/backend/vif/27/1
2   0  00:16:3e:4d:2f:0e    2     4      7     1792 /1793 
/local/domain/0/backend/vif/27/2
3   0  00:16:3e:11:35:e0    3     6      -1    -1   /-1 
/local/domain/0/backend/vif/27/3
The test environment is as follows.
- xen-unstable.hg : cs15072
- DomVTx(X86) with PV-ON-HVM

This problem was investigated a little.
The cause is not to be able to execute HYPERVISOR_grant_table_op from the hvm 
domain.
Therefore, the number of boot_max_nr_grant_frames is four.

・unmodified_drivers/linux-2.6/platform-pci/platform-pci.c
　　platform_pci_init()
 -> ・linux-2.6-xen-sparse/drivers/xen/core/gnttab.c
    　 gnttab_init()
       　  __max_nr_grant_frames()

The size of the grant table is acquired here.

404  static unsigned int __max_nr_grant_frames(void)
405  {
406          struct gnttab_query_size query;
407          int rc;
408
409          query.dom = DOMID_SELF;
410
411          rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);　<<== 
This
412          if ((rc < 0) || (query.status != GNTST_okay))
413                  return 4; /* Legacy max supported number of frames */
414
415          return query.max_nr_frames;
416  }

=> ・xen/arch/x86/hvm/hvm.c
736  int hvm_do_hypercall(struct cpu_user_regs *regs)
737  {
...
759      if ( (eax >= NR_hypercalls) || !hvm_hypercall32_table[eax] )
760      {
761          if ( eax != __HYPERVISOR_grant_table_op )
762              gdprintk(XENLOG_WARNING, "HVM vcpu %d:%d bad hypercall %u.\n",
763                       current->domain->domain_id, current->vcpu_id, eax);
764          regs->eax = -ENOSYS;
765          return HVM_HCALL_completed;
766      }

hvm_hypercall32_table is as follows.
Therefore, grant_table_op cannot be called.

726  static hvm_hypercall_t *hvm_hypercall32_table[NR_hypercalls] = {
727      HYPERCALL_COMPAT32(memory_op),
728      HYPERCALL(xen_version),
729      HYPERCALL(event_channel_op),
730      HYPERCALL(sched_op),
731      HYPERCALL(hvm_op)
732  };

Cannot grant_table_op make it call from the hvm domain?

How should we correct it if so?

Best Regard,

--
Takanori Kasai 


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