Re: [Xen-devel] Support for mii_xxx functions?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> One the receive side the code compiles as is, but I have not yet verified if
> the interface it calls -- eth_copy_and_sum() -- will work, or if I need to
> changed it to somehting like this:
> 
> >  vdata = map_domain_mem(skb->data);
> >  copy 'len' bytes to 'vdata' from NIC buffer
> >  unmap_domain_mem(vdata);
> >  skb_put(len);
> 
> as you suggested.  If you (or anyone else) has any thoughts on why this (and
> other) skbuff interfaces where not supported in Xen, that would help with my
> digging.  Remember, I'm not at all familiar with the linux kernel source so
> I have to read it all to know what anything is doing... on the other hand it
> is just time and code...

You will have to change it. Any function which will access the packet
data must use map_domain_mem(), as the data pointer within the skbuff
is not usable directly by Xen.

Note that some skb_* functions already do the map_domain_mem() for you
--- any skb copying function based on skb_copy_bits() is safe.

Note also that we hope fairly soon (within the next few months) to
move all device drivers into "I/O domains" running outside of Xen in
ring 1. At that point we will hopefully be able to run Linux device
drivers unmodified, so this porting pain will no longer be necessary
:-)

 -- Keir


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