Re: [Minios-devel] Can't map grant_table between domains

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Aug 01, 2016 at 03:11:48PM +0100, gotoc io wrote:
> Hi I was trying to make communication between Two mini-os domains.
> I have offerer and mapper domains, offerer has ID=A, mapper has ID=B.
> 
> 
> Offerer function:
> 
>         setup_op.dom = DOMID_SELF;
>         setup_op.nr_frames = 1;
>         setup_op.frame_list = (uint64_t*)grant_table;
>         HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup_op, 1);

OOI why do you setup grant table again?

>         grant_table[0].domid = B;
>         grant_table[0].frame = *shared_page >> 12;
>         flags = GTF_permit_access & GTF_reading & GTF_writing;
>         grant_table[0].flags = flags;
> 

Maybe missing some memory barriers?

See gnttab.c:gnttab_grant_access.

> 
> Mapping function:
> 
>         gnttab_map_grant_ref_t map_op;
>         map_op.host_addr = (uint64_t)shared_page;
>         map_op.flags = GNTMAP_host_map;
>         map_op.ref = entry;
>         map_op.dom = A;
>         HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &map_op,1);

This looks reasonable to me.

> 
> After that I always got map_op.status == -1
> More over when I run xl dmesg I got followed error:
> 
> (XEN) grant_table.c:830:d28v0 Bad domain (0 != B), or risk of counter
> overflow 00000002, or subpage 0
> 
> 
> Any idea what I can do in wrong way? I was trying to follow way how vTPM
> driver is working but after faced this error I can't move forward.
> 

In any case, there is already a set of API that you can use from
gnttab.c and gntmap.c. Why not just use those?

Wei.

> Thanks for any help.

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