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    SubjectRE: [PATCH RFC 01/11] iommu: Add pasid_bits field in struct dev_iommu
    Date
    > From: Lu Baolu <baolu.lu@linux.intel.com>
    > Sent: Sunday, March 20, 2022 2:40 PM
    >
    > Use this field to save the pasid/ssid bits that a device is able to
    > support with its IOMMU hardware. It is a generic attribute of a device
    > and lifting it into the per-device dev_iommu struct 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 features are enabled on the devices.
    >
    > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
    > ---
    > include/linux/iommu.h | 1 +
    > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 +
    > drivers/iommu/intel/iommu.c | 5 ++++-
    > 3 files changed, 6 insertions(+), 1 deletion(-)
    >
    > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
    > index 6ef2df258673..36f43af0af53 100644
    > --- a/include/linux/iommu.h
    > +++ b/include/linux/iommu.h
    > @@ -368,6 +368,7 @@ struct dev_iommu {
    > struct iommu_fwspec *fwspec;
    > struct iommu_device *iommu_dev;
    > void *priv;
    > + unsigned int pasid_bits;
    > };
    >
    > int iommu_device_register(struct iommu_device *iommu,
    > 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 627a3ed5ee8f..8e262210b5ad 100644
    > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
    > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
    > @@ -2812,6 +2812,7 @@ static int arm_smmu_dev_enable_feature(struct
    > device *dev,
    > master->iopf_enabled = true;
    > return 0;
    > case IOMMU_DEV_FEAT_SVA:
    > + dev->iommu->pasid_bits = master->ssid_bits;
    > return arm_smmu_master_enable_sva(master);
    > default:
    > return -EINVAL;
    > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
    > index 6f7485c44a4b..c1b91bce1530 100644
    > --- a/drivers/iommu/intel/iommu.c
    > +++ b/drivers/iommu/intel/iommu.c
    > @@ -4587,8 +4587,11 @@ static struct iommu_device
    > *intel_iommu_probe_device(struct device *dev)
    > if (pasid_supported(iommu)) {
    > int features = pci_pasid_features(pdev);
    >
    > - if (features >= 0)
    > + if (features >= 0) {
    > info->pasid_supported = features | 1;
    > + dev->iommu->pasid_bits =
    > + fls(pci_max_pasids(pdev)) - 1;

    Original intel_svm_alloc_pasid() covers both PCI and non-PCI devices:

    ioasid_t max_pasid = dev_is_pci(dev) ?
    pci_max_pasids(to_pci_dev(dev)) : intel_pasid_max_id;

    though I'm not sure whether non-PCI SVA has been supported indeed, this
    patch implies a functional change here.

    > + }
    > }
    >
    > if (info->ats_supported && ecap_prs(iommu->ecap)
    > &&
    > --
    > 2.25.1

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