[PATCH v3] iommu/vt-d: Fix PASID directory pointer coherency

[Jacob Pan]

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 clflush calls whenever allocating and updating
a PASID table directory to ensure cache coherency.

On the reverse direction, there's no need to clflush 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.
PASID directory entries are also never freed once allocated.

[    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@xxxxxxxxxxxxxxx>
Fixes: 0bbeb01a4faf ("iommu/vt-d: Manage scalalble mode PASID tables")
Reported-by: Sukumar Ghorai <sukumar.ghorai@xxxxxxxxx>
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
v3: Add clflush after PASID directory allocation to prevent malicious
device attack with unauthorized PASIDs. Also flush all the PASID entries
after directory updates. (Baolu)
v2: Add clflush to PASID directory update case (Baolu, Kevin review)
---
 drivers/iommu/intel/iommu.c | 2 ++
 drivers/iommu/intel/pasid.c | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 59df7e42fd53..161342e7149d 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1976,6 +1976,8 @@ 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);
+		if (!ecap_coherent(iommu->ecap))
+			clflush_cache_range(table->table, sizeof(u64));
 
 		/* Setup the RID_PASID field: */
 		context_set_sm_rid2pasid(context, PASID_RID2PASID);
diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index fb3c7020028d..979f796175b1 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -128,6 +128,9 @@ int intel_pasid_alloc_table(struct device *dev)
 	pasid_table->max_pasid = 1 << (order + PAGE_SHIFT + 3);
 	info->pasid_table = pasid_table;
 
+	if (!ecap_coherent(info->iommu->ecap))
+		clflush_cache_range(pasid_table->table, size);
+
 	return 0;
 }
 
@@ -215,6 +218,10 @@ static struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid)
 			free_pgtable_page(entries);
 			goto retry;
 		}
+		if (!ecap_coherent(info->iommu->ecap)) {
+			clflush_cache_range(entries, VTD_PAGE_SIZE);
+			clflush_cache_range(&dir[dir_index].val, sizeof(*dir));
+		}
 	}
 
 	return &entries[index];
-- 
2.25.1