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Re: [Xen-devel] netif & grant tables

To: Matt Chapman <matthewc@xxxxxx>
Subject: Re: [Xen-devel] netif & grant tables
From: Stefan Berger <stefanb@xxxxxxxxxx>
Date: Fri, 1 Jul 2005 16:29:20 -0400
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xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote on 06/30/2005 10:28:54 PM:

> Hi,
> I'm currently looking at getting domU networking working
> on IA64, and to do this I need to make netback/netfront
> use grant tables.

You *probably* won't get this to work right out of the box. On i386 it 
fails due to dom Us not becoming privileged and so a check like IS_PRIV() 
fails in xen/common/grant_table.c line 692 and probably somewhere else 
also. The question is how this should be fixed. Should the HV call to 
create a domain receive an additional parameter including flags that 
should be set in a domain, such as for example the _DOMF_privileged? 
Currently this flag only seems to be set in one place for dom 0.

The quick fix is:
        set_bit(_DOMF_privileged, &d->domain_flags) 

before the 'return d' in do_createdomain() in xen/common/domain.c -> it 
will make all domains privileged 

To compile the backends into a domU I had to activate 
file of the dom U kernel for having alloc_empty_lowmem_region() compiled 
into th kernel (arch/xen/i386/mm/hypervisor.c). Is this call to 
alloc_empty_lowmem_region() necessary or would another memory allocation 
routine work as well. All the backends seem to use it, though.

> I'm told that there's already a patch floating around,
> can someone tell me where to find it?
> Matt
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