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Re: [Xen-devel] [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT

On 2014/7/30 18:47, Jan Beulich wrote:
On 30.07.14 at 12:40, <tiejun.chen@xxxxxxxxx> wrote:
On 2014/7/30 18:25, Jan Beulich wrote:
On 30.07.14 at 11:40, <tiejun.chen@xxxxxxxxx> wrote:
   From what those codes mean, it just return regardless whether they
really conflict. And this is just a good assumption, so if I'm
understanding this properly, actually our patches do this thing
precisely because we further check if this assumption is true, then take
necessary actions.

Except that the pointed out check prevents the code you modify
from being reached at all, i.e. as long as that check is there it
doesn't matter (for any passed through USB device) what action
rmrr_identity_mapping() takes.

Sorry, what do you mean?

  From my point of view these two patches should be better than drop
simply RMRR for any PT USB device no matter if its really necessary.

I mean that for USB devices your patches change nothing without
said check also getting removed.


For USB instance, I think currently we still keep that until we have a complete solution since this is always safe.

Additionally, I'm trying to figure out that solution. As I mentioned previously, I think we can reserve all RMRR once when a guest call XENMEM_machine_memory_map to create its own memory. What about this idea? Or other better suggestions?


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