[Xen-devel] Problem when doing direct_remap_area_pages() in a privileged user domain

[Stefan Berger <stefanb@xxxxxxxxxx>]

Hi!

  I have come accross a problem when trying to do a 
direct_remap_area_pages() call in a backend driver that is running in a 
privileged user domain. The call ends up with an error code (-14 = 
-EFAULT). This in turn is caused by the hypervisor call 
HYPERVISOR_mmu_update() which returns an error code of -22 = -EINVAL after 
failing in set_foreigndom due to not (!?!) being privileged. The same call 
returns no error if run in domain-0.
  However, I found the solution to fix this. I needed to make a fake(*) 
PCI device available to the privileged user domain by adding a line like 
pci=['00,07,00'] to the configuration file, because this would actually 
set the privileged flag for the domain in 
xen/common/physdev.c:physdev_pci_access_modify(). I wonder whether the 
setting of this flag should not be moved to some other place?

(*): fake, because I don't really need access to a PCI device in that 
domain

Regards,
   Stefan

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