iommu/vt-d: Update scalable mode paging structure coherency

iommu/vt-d: Update scalable mode paging structure coherency

BugLink: https://bugs.launchpad.net/bugs/1885942
[ Upstream commit 04c00956ee3cd138fd38560a91452a804a8c5550 ]

The Scalable-mode Page-walk Coherency (SMPWC) field in the VT-d extended
capability register indicates the hardware coherency behavior on paging
structures accessed through the pasid table entry. This is ignored in
current code and using ECAP.C instead which is only valid in legacy mode.
Fix this so that paging structure updates could be manually flushed from
the cache line if hardware page walking is not snooped.

Fixes: 765b6a98c1de3 ("iommu/vt-d: Enumerate the scalable mode capability")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lore.kernel.org/r/20200622231345.29722-6-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>