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[Xen-devel] question on iommu _map_page

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Kaushik Kumar Ram <kaushik@xxxxxxxx>
  • Date: Thu, 27 May 2010 15:37:10 -0500
  • Delivery-date: Thu, 27 May 2010 13:38:10 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hi all,

I am trying to use the VT-d support with a PV driver domain which performs 
network I/O on behalf of guest domains. 
When I initiate any network I/O it results in I/O page faults. On taking a 
closer look I find that iommu_map_page() is called only for writable pages from 
__gnttab_map_grant_ref(). This results in page faults during packet 
transmission since pages are mapped read-only in this case. 
When I remove this restriction, I can get it working without any page faults. 

Is this a bug? or am I missing something here? I am using the latest unstable 
version of Xen. This part of the source code hasn't changed in a long time.

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