Re: [PATCH v2 8/8] iommu/arm-smmu-v3: Add support for PCI PASID

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Fri, 8 Nov 2019 16:25:08 +0100
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:

> Enable PASID for PCI devices that support it. Since the SSID tables are
> allocated by arm_smmu_attach_dev(), PASID has to be enabled early enough.
> arm_smmu_dev_feature_enable() would be too late, since by that time the
> main DMA domain has already been attached. Do it in add_device() instead.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Seems straightforward.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Thanks for working on this stuff.  I hope we an move to get the rest of the
SVA elements lined up behind it so everything moves quickly in the next
cycle (or two).

Jonathan

> ---
>  drivers/iommu/arm-smmu-v3.c | 51 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 88ec0bf33492..3ee313c08325 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2633,6 +2633,49 @@ static void arm_smmu_disable_ats(struct arm_smmu_master *master)
>  	atomic_dec(&smmu_domain->nr_ats_masters);
>  }
>  
> +static int arm_smmu_enable_pasid(struct arm_smmu_master *master)
> +{
> +	int ret;
> +	int features;
> +	int num_pasids;
> +	struct pci_dev *pdev;
> +
> +	if (!dev_is_pci(master->dev))
> +		return -ENOSYS;
> +
> +	pdev = to_pci_dev(master->dev);
> +
> +	features = pci_pasid_features(pdev);
> +	if (features < 0)
> +		return -ENOSYS;
> +
> +	num_pasids = pci_max_pasids(pdev);
> +	if (num_pasids <= 0)
> +		return -ENOSYS;
> +
> +	ret = pci_enable_pasid(pdev, features);
> +	if (!ret)
> +		master->ssid_bits = min_t(u8, ilog2(num_pasids),
> +					  master->smmu->ssid_bits);
> +	return ret;
> +}
> +
> +static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
> +{
> +	struct pci_dev *pdev;
> +
> +	if (!dev_is_pci(master->dev))
> +		return;
> +
> +	pdev = to_pci_dev(master->dev);
> +
> +	if (!pdev->pasid_enabled)
> +		return;
> +
> +	master->ssid_bits = 0;
> +	pci_disable_pasid(pdev);
> +}
> +
>  static void arm_smmu_detach_dev(struct arm_smmu_master *master)
>  {
>  	unsigned long flags;
> @@ -2841,13 +2884,16 @@ static int arm_smmu_add_device(struct device *dev)
>  
>  	master->ssid_bits = min(smmu->ssid_bits, fwspec->num_pasid_bits);
>  
> +	/* Note that PASID must be enabled before, and disabled after ATS */
> +	arm_smmu_enable_pasid(master);
> +
>  	if (!(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB))
>  		master->ssid_bits = min_t(u8, master->ssid_bits,
>  					  CTXDESC_LINEAR_CDMAX);
>  
>  	ret = iommu_device_link(&smmu->iommu, dev);
>  	if (ret)
> -		goto err_free_master;
> +		goto err_disable_pasid;
>  
>  	group = iommu_group_get_for_dev(dev);
>  	if (IS_ERR(group)) {
> @@ -2860,6 +2906,8 @@ static int arm_smmu_add_device(struct device *dev)
>  
>  err_unlink:
>  	iommu_device_unlink(&smmu->iommu, dev);
> +err_disable_pasid:
> +	arm_smmu_disable_pasid(master);
>  err_free_master:
>  	kfree(master);
>  	fwspec->iommu_priv = NULL;
> @@ -2880,6 +2928,7 @@ static void arm_smmu_remove_device(struct device *dev)
>  	arm_smmu_detach_dev(master);
>  	iommu_group_remove_device(dev);
>  	iommu_device_unlink(&smmu->iommu, dev);
> +	arm_smmu_disable_pasid(master);
>  	kfree(master);
>  	iommu_fwspec_free(dev);
>  }