passthrough: always use hw intx and always get it from the same place

passthrough: always use hw intx and always get it from the same place

The assumption that function zero always uses INTA tuns out not
to be true in the wild. This leaves us with three options.

1) Always use INTA

   This was the case before multi-function pass-through was possible.
   But with the advent of multi-function pass-through this may lead
   to excessive virtual GSI sharing.

2) Fix emulation to use INTA for function zero

3) Always use the hardware value for INTx

There doesn't seem to be much between 2) and 3) but the latter seems
slightly cleaner so I advocate that approach.

Cc: Tom Rotenberg <tom.rotenberg@gmail.com>
Cc: Edwin Zhai <edwin.zhai@intel.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
[patch 2/2] qemu-xen: pass-through: always use hw intx

From:

[patch 0/2] qemu-xen: pass-through: always use hw intx
pass-through: always use hw intx and always get it from the same place

The assumption that function zero always uses INTA tuns out not
to be true in the wild. This leaves us with three options.

1) Always use INTA

   This was the case before multi-function pass-through was possible.
   But with the advent of multi-function pass-through this may lead
   to excessive virtual GSI sharing.

2) Fix emulation to use INTA for function zero

3) Always use the hardware value for INTx

There doesn't seem to be much between 2) and 3) but the latter seems
slightly cleaner so I advocate that approach.