ACRN disables Snoop Control in VT-d DMAR engines for simplifing the
implementation. Also, since the snoop behavior of PCIE transactions
can be controlled by guest drivers, some devices may take the advantage
of the NO_SNOOP_ATTRIBUTE of PCIE transactions for better performance
when snoop is not needed. No matter ACRN enables or disables Snoop
Control, the DMA operations of passthrough devices behave correctly
from guests' point of view.
This patch is used to clean all the snoop related code.
Tracked-On: #4509
Signed-off-by: Xiaoguang Wu <xiaoguang.wu@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@intel.com>
Acked-by: Eddie Dong <eddie.dong@Intel.com>
d4f789f47e