RE: [PATCH v7 01/10] iommu: Add pasids field in struct iommu_device

Tian, Kevin
2022-05-24T09:24:53Z

> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Thursday, May 19, 2022 3:21 PM
>
> 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.lu@linux.intel.com>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@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;

max_pasid or nr_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;
> +

supported pasid bits is reported by ecap_pss(). I don't think we should
assume 20bits here.

> /*
> * 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