Xen devel - May 2007 - [PATCH] Fix expandable grant table for x86

Hi All,

We contributed this problem that the grant table was not able to be expanded 
before.

We corrected that HYPERCALL of grant_table_op was able to be called
from the HVM domain with x86.
It was confirmed to be able to expand grant table by this patch.
It is not tested things except the acquisition of the query size.

It seems that the structure of HYPERCALL is the same excluding
GNTTABOP_setup_table as 32 bits and 64 bits.
When it was not hvm domain, GNTTABOP_setup_table returned ENOSYS.

Signed-off-by: Takanori Kasai <kasai.takanori@jp.fujitsu.com>
Signed-off-by: Tsunehisa Doi <Doi.Tsunehisa@jp.fujitsu.com>

Best Regards,

--
Takanori Kasai

----- Original Message ----- 
From: "Kasai Takanori" <kasai.takanori@jp.fujitsu.com>
To: "xen-devel" <xen-devel@lists.xensource.com>
Sent: Thursday, May 24, 2007 8:50 PM
Subject: [Xen-devel] expandable grant table bug?

> 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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