On 04/03/2015 15:29, Catalin Marinas wrote:

I disagree it is 100% a host-side issue. It is a host-side issue _if_
the host tells the guest that the (virtual) device is non-coherent (or,
more precisely, it does not explicitly tell the guest that the device is
coherent). If the guest thinks the (virtual) device is non-coherent
because of information passed by the host, I fully agree that the host
needs to manage the cache coherency.

However, the host could also pass a "dma-coherent" property in the DT
given to the guest and avoid any form of cache maintenance. If the guest
does not honour such coherency property, it's a guest problem and it
needs fixing in the guest. This isn't any different from a real physical
device behaviour.

Can you add that property to the device tree for PCI devices too?

Paolo