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 activating 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@vger.kernel.org Fixes: 0bbeb01a4faf ("iommu/vt-d: Manage scalalble mode PASID tables") 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 --- v2: Add clflush to PASID directory update case (Baolu, Kevin review) --- drivers/iommu/intel/iommu.c | 2 ++ drivers/iommu/intel/pasid.c | 2 ++ 2 files changed, 4 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..bcb2e6f23742 100644 --- a/drivers/iommu/intel/pasid.c +++ b/drivers/iommu/intel/pasid.c @@ -216,6 +216,8 @@ static struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid) goto retry; } } + if (!ecap_coherent(info->iommu->ecap)) + clflush_cache_range(&dir[dir_index], sizeof(u64));
return &entries[index]; }