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Re: [Xen-devel] [PATCH v7 10/10] xen/common: do not implicitly permit access to mapped I/O memory

On 26/05/14 12:14, Jan Beulich wrote:
On 26.05.14 at 12:53, <julien.grall@xxxxxxxxxx> wrote:

On 26/05/14 11:14, Jan Beulich wrote:

Or maybe I wasn't wrong - the patch context doesn't really make
clear whether it's the granting or mapping operation that gets
adjusted here (since an earlier patch moved the mapping one into
this function).

           ret = -EPERM;
-        if ( !iomem_access_permitted(current->domain, mfn, mfn_end) )
+        if ( !iomem_access_permitted(d, mfn, mfn_end) )

           ret = xsm_iomem_mapping(XSM_HOOK, d, mfn, mfn_end, add);

There is an xsm_iomem_mapping just after, so the change has been done in

In which case I indeed stick to my original comment - it's perhaps
best to check _both_.

Why? We may want to map the region in the guest P2M without giving the permission to the guest (I'm thinking about ARM passthrough case).

With your requirements, we have to call 2 hypercalls rather than one for memory mapping, even if we don't want to allow the guest modifying iomem range.


Julien Grall

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