[PATCH] iommu/vt-d: Fix PASID directory pointer coherency

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

On platforms that do not support IOMMU Extended capability bit 0
Page-walk Coherency, CPU caches are not snooped when IOMMU is accessing
any translation structures. IOMMU access goes only directly to
memory. Intel IOMMU code was missing a flush for the PASID table
directory that resulted in the unrecoverable fault as shown below.

This patch adds a clflush when activating a PASID table directory.
There's no need to do clflush of the PASID directory pointer when we
deactivate a context entry in that IOMMU hardware will not see the old
PASID directory pointer after we clear the context entry.

[    0.555386] DMAR: DRHD: handling fault status reg 3
[    0.555805] DMAR: [DMA Read NO_PASID] Request device [00:0d.2] fault addr 0x1026a4000 [fault reason 0x51] SM: Present bit in Directory Entry is clear
[    0.556348] DMAR: Dump dmar1 table entries for IOVA 0x1026a4000
[    0.556348] DMAR: scalable mode root entry: hi 0x0000000102448001, low 0x0000000101b3e001
[    0.556348] DMAR: context entry: hi 0x0000000000000000, low 0x0000000101b4d401
[    0.556348] DMAR: pasid dir entry: 0x0000000101b4e001
[    0.556348] DMAR: pasid table entry[0]: 0x0000000000000109
[    0.556348] DMAR: pasid table entry[1]: 0x0000000000000001
[    0.556348] DMAR: pasid table entry[2]: 0x0000000000000000
[    0.556348] DMAR: pasid table entry[3]: 0x0000000000000000
[    0.556348] DMAR: pasid table entry[4]: 0x0000000000000000
[    0.556348] DMAR: pasid table entry[5]: 0x0000000000000000
[    0.556348] DMAR: pasid table entry[6]: 0x0000000000000000
[    0.556348] DMAR: pasid table entry[7]: 0x0000000000000000
[    0.556348] DMAR: PTE not present at level 4

Cc: <stable@vger.kernel.org>
Reported-by: Sukumar Ghorai <sukumar.ghorai@intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 drivers/iommu/intel/iommu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 59df7e42fd53..b4878c7ac008 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1976,6 +1976,12 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 		pds = context_get_sm_pds(table);
 		context->lo = (u64)virt_to_phys(table->table) |
 				context_pdts(pds);
+		/*
+		 * Scalable-mode PASID directory pointer is not snooped if the
+		 * coherent bit is not set.
+		 */
+		if (!ecap_coherent(iommu->ecap))
+			clflush_cache_range(table->table, sizeof(void *));
 
 		/* Setup the RID_PASID field: */
 		context_set_sm_rid2pasid(context, PASID_RID2PASID);
-- 
2.25.1