[PATCH 1/5] xen/arm: smmuv1: Handle stream IDs more dynamically

[Rahul Singh <rahul.singh@xxxxxxx>]

Backport commit 21174240e4f4439bb8ed6c116cdbdc03eba2126e
"iommu/arm-smmu: Handle stream IDs more dynamically" from the Linux
ernel.

This patch is the preparatory work to fix the stream match conflict
when two devices have the same stream-id.

Original commit message:

Rather than assuming fixed worst-case values for stream IDs and SMR
masks, keep track of whatever implemented bits the hardware actually
reports. This also obviates the slightly questionable validation of SMR
fields in isolation - rather than aborting the whole SMMU probe for a
hardware configuration which is still architecturally valid, we can
simply refuse masters later if they try to claim an unrepresentable ID
or mask (which almost certainly implies a DT error anyway).

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
 xen/drivers/passthrough/arm/smmu.c | 43 +++++++++++++++---------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/xen/drivers/passthrough/arm/smmu.c 
b/xen/drivers/passthrough/arm/smmu.c
index 3e8aa37866..adfab8ee84 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -440,9 +440,7 @@ static struct iommu_group *iommu_group_get(struct device 
*dev)
 #define ARM_SMMU_GR0_SMR(n)            (0x800 + ((n) << 2))
 #define SMR_VALID                      (1U << 31)
 #define SMR_MASK_SHIFT                 16
-#define SMR_MASK_MASK                  0x7fff
 #define SMR_ID_SHIFT                   0
-#define SMR_ID_MASK                    0x7fff
 
 #define ARM_SMMU_GR0_S2CR(n)           (0xc00 + ((n) << 2))
 #define S2CR_CBNDX_SHIFT               0
@@ -632,6 +630,8 @@ struct arm_smmu_device {
        atomic_t                        irptndx;
 
        u32                             num_mapping_groups;
+       u16                             streamid_mask;
+       u16                             smr_mask_mask;
        DECLARE_BITMAP(smr_map, ARM_SMMU_MAX_SMRS);
 
        unsigned long                   s1_input_size;
@@ -2140,39 +2140,40 @@ static int arm_smmu_device_cfg_probe(struct 
arm_smmu_device *smmu)
                dev_notice(smmu->dev, "\tcoherent table walk\n");
        }
 
+       /* Max. number of entries we have for stream matching/indexing */
+       size = 1 << ((id >> ID0_NUMSIDB_SHIFT) & ID0_NUMSIDB_MASK);
+       smmu->streamid_mask = size - 1;
        if (id & ID0_SMS) {
-               u32 smr, sid, mask;
+               u32 smr;
 
                smmu->features |= ARM_SMMU_FEAT_STREAM_MATCH;
-               smmu->num_mapping_groups = (id >> ID0_NUMSMRG_SHIFT) &
-                                          ID0_NUMSMRG_MASK;
-               if (smmu->num_mapping_groups == 0) {
+               size = (id >> ID0_NUMSMRG_SHIFT) & ID0_NUMSMRG_MASK;
+               if (size == 0) {
                        dev_err(smmu->dev,
                                "stream-matching supported, but no SMRs 
present!\n");
                        return -ENODEV;
                }
 
-               smr = SMR_MASK_MASK << SMR_MASK_SHIFT;
-               smr |= (SMR_ID_MASK << SMR_ID_SHIFT);
+               /*
+                * SMR.ID bits may not be preserved if the corresponding MASK
+                * bits are set, so check each one separately. We can reject
+                * masters later if they try to claim IDs outside these masks.
+                */
+               smr = smmu->streamid_mask << SMR_ID_SHIFT;
                writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
                smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+               smmu->streamid_mask = smr >> SMR_ID_SHIFT;
 
-               mask = (smr >> SMR_MASK_SHIFT) & SMR_MASK_MASK;
-               sid = (smr >> SMR_ID_SHIFT) & SMR_ID_MASK;
-               if ((mask & sid) != sid) {
-                       dev_err(smmu->dev,
-                               "SMR mask bits (0x%x) insufficient for ID field 
(0x%x)\n",
-                               mask, sid);
-                       return -ENODEV;
-               }
+               smr = smmu->streamid_mask << SMR_MASK_SHIFT;
+               writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
+               smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+               smmu->smr_mask_mask = smr >> SMR_MASK_SHIFT;
 
                dev_notice(smmu->dev,
-                          "\tstream matching with %u register groups, mask 
0x%x\n",
-                          smmu->num_mapping_groups, mask);
-       } else {
-               smmu->num_mapping_groups = (id >> ID0_NUMSIDB_SHIFT) &
-                                          ID0_NUMSIDB_MASK;
+                          "\tstream matching with %lu register groups, mask 
0x%x",
+                          size, smmu->smr_mask_mask);
        }
+       smmu->num_mapping_groups = size;
 
        /* ID1 */
        id = readl_relaxed(gr0_base + ARM_SMMU_GR0_ID1);
-- 
2.17.1