Use this field to keep the number of supported PASIDs that an IOMMU
hardware is able to support. This is a generic attribute of an IOMMU
and lifting it into the per-IOMMU device structure makes it possible
to allocate a PASID for device without calls into the IOMMU drivers.
Any iommu driver which suports PASID related features should set this
field before enabling them on the devices.

Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
Reviewed-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
---
 include/linux/iommu.h                       | 2 ++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 +
 drivers/iommu/intel/dmar.c                  | 4 ++++
 3 files changed, 7 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5e1afe169549..da423e87f248 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -318,12 +318,14 @@ struct iommu_domain_ops {
  * @list: Used by the iommu-core to keep a list of registered iommus
  * @ops: iommu-ops for talking to this iommu
  * @dev: struct device for sysfs handling
+ * @pasids: number of supported PASIDs
  */
 struct iommu_device {
        struct list_head list;
        const struct iommu_ops *ops;
        struct fwnode_handle *fwnode;
        struct device *dev;
+       u32 pasids;
 };
 
 /**
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c 
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 88817a3376ef..6e2cd082c670 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3546,6 +3546,7 @@ static int arm_smmu_device_hw_probe(struct 
arm_smmu_device *smmu)
        /* SID/SSID sizes */
        smmu->ssid_bits = FIELD_GET(IDR1_SSIDSIZE, reg);
        smmu->sid_bits = FIELD_GET(IDR1_SIDSIZE, reg);
+       smmu->iommu.pasids = smmu->ssid_bits;
 
        /*
         * If the SMMU supports fewer bits than would fill a single L2 stream
diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 4de960834a1b..1c3cf267934d 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1126,6 +1126,10 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
        raw_spin_lock_init(&iommu->register_lock);
 
+       /* Supports full 20-bit PASID in scalable mode. */
+       if (ecap_pasid(iommu->ecap))
+               iommu->iommu.pasids = 1UL << 20;
+
        /*
         * This is only for hotplug; at boot time intel_iommu_enabled won't
         * be set yet. When intel_iommu_init() runs, it registers the units
-- 
2.25.1

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