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Re: [Xen-devel] Grant Table problem mapping dom0 mem to domU Derek Murray Thu Jul 26 18:01:45 2007

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.


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?

C. René

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