Re: [Xen-devel] Grant Table problem mapping dom0 mem to domU

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

Hi Carlos,

The problem you are facing is that the grant_operation_permitted()  
test (in the GNTTABOP_map_grant_ref case of the do_grant_table_op  
function in xen/common/grant_table.c) is failing. At present, only  
domains with iomem permissions can map grant references: typically,  
the only such domain is dom0. This is due to a TLB flush issue which  
was addressed in a recent patchset from Kieran Mansley. You can  
either try giving some dummy iomem privileges to your domU, or change  
the definition of grant_operation_permitted(d) to 1, so that it  
always succeeds.
Regards,

Derek Murray.

On 25 Jul 2007, at 16:41, Carlos Perez wrote:

> I've been looking through some back-end drivers and I notice that
> grant tables are used to map domU memory into the privileged domain,
> is the opposite possible? Can I map dom0 memory into a domU?
>
> I've written code grants foreign access to a page from dom0 (take the
> grant ref_id) then on domU I try to map it (basically the same way ex
> blkback does it, or just any other driver for that matter) and all I
> get from HYPERVISOR_grant_table_op() is a -1 return value, op.status
> is empty=0.
>
> I'll send more information on the specific error, if I at least know
> that this can be done and I'm just not falling of a cliff. Also, if it
> is possible, can you point me to some example code?
>
> thanks,
> C. René
>
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