Re: [Xen-devel] Cannot get shared page in domU

[Xin Jin <jxinpku@xxxxxxxxx>]

In

share_mem->gref = gnttab_grant_foreign_access(domid_remote, virt_to_mfn(share_mem), 0);

I have explicitly specified the domid that can use the gref as "domid_remote".

What else can be wrong?

On Thu, Nov 10, 2011 at 12:09 AM, Daniel Castro <evil.dani@xxxxxxxxx> wrote:

On Thu, Nov 10, 2011 at 1:15 PM, Xin Jin <jxinpku@xxxxxxxxx> wrote:
> Hi, I cannot get a shared page in domU.
> In a domU, I used the folloing code to grant a page to another domU.
> share_mem = (share_mem_desp *) __get_free_page(GFP_KERNEL);
> share_mem->gref = gnttab_grant_foreign_access(domid_remote,
> virt_to_mfn(share_mem), 0);
> In another domU, I used the folloing code to get the shared page.
> share_vmarea = alloc_vm_area(PAGE_SIZE);
> gnttab_set_map_op( &map_op, (unsigned long)share_vmarea->addr,
> GNTMAP_host_map, gref, domid_remote );
> HYPERVISOR_grant_table_op( GNTTABOP_map_grant_ref, &map_op, 1 );
> While using the exactly same code to get the shared page in dom0, it woks
> all well. But it cannot work in domU.
> I use Xen 4.1.1 and fedora 14 ( linux 3.1.0 both for dom0 and domU ).
> Can anyone help me?

On the interface struct when you issue the hypercall you need to
specify the domid that can use the gref. Maybe the default is domid 0.
The struct grant_entry_v1 has member domid for the foreign guest,
check that value.

> Thanks!
> -- Xin
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
>
>



--
+-=====---------------------------+
| +---------------------------------+ | This space intentionally blank
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| |   | Daniel Castro,                |
| |   | Consultant/Programmer.|
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--
Xin JIN

PhD student
Department of Computer Science

Princeton University

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