Re: [PATCH v2 3/6] iommu/vt-d: Make intel_iommu_set_dev_pasid() to handle domain replacement

[Baolu Lu <baolu.lu@linux.intel.com>]

On 9/12/24 9:04 PM, Yi Liu wrote:
> set_dev_pasid op is going to support domain replacement and keep the old
> hardware config if it fails. Make the Intel iommu driver be prepared for
> it.
> 
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 98 ++++++++++++++++++++++++-------------
>   1 file changed, 65 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 80b587de226d..6f5a8e549f3f 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4248,8 +4248,8 @@ static int intel_iommu_iotlb_sync_map(struct iommu_domain *domain,
>   	return 0;
>   }
>   
> -static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
> -					 struct iommu_domain *domain)
> +static void domain_remove_dev_pasid(struct iommu_domain *domain,
> +				    struct device *dev, ioasid_t pasid)
>   {
>   	struct device_domain_info *info = dev_iommu_priv_get(dev);
>   	struct dev_pasid_info *curr, *dev_pasid = NULL;
> @@ -4257,11 +4257,6 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
>   	struct dmar_domain *dmar_domain;
>   	unsigned long flags;
>   
> -	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
> -		intel_pasid_tear_down_entry(iommu, dev, pasid, 0);
> -		return;
> -	}
> -
>   	dmar_domain = to_dmar_domain(domain);
>   	spin_lock_irqsave(&dmar_domain->lock, flags);
>   	list_for_each_entry(curr, &dmar_domain->dev_pasids, link_domain) {
> @@ -4278,13 +4273,24 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
>   	domain_detach_iommu(dmar_domain, iommu);
>   	intel_iommu_debugfs_remove_dev_pasid(dev_pasid);
>   	kfree(dev_pasid);
> +}
> +
> +static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
> +					 struct iommu_domain *domain)
> +{
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct intel_iommu *iommu = info->iommu;
> +
>   	intel_pasid_tear_down_entry(iommu, dev, pasid,
>   				    INTEL_PASID_TEARDOWN_DRAIN_PRQ);
> +	if (domain->type == IOMMU_DOMAIN_IDENTITY)
> +		return;

The static identity domain is not capable of handling page requests.
Therefore there is no need to drain PRQ for an identity domain removal.

So it probably should be something like this:

	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
		intel_pasid_tear_down_entry(iommu, dev, pasid, 0);
		return;
	}

	intel_pasid_tear_down_entry(iommu, dev, pasid,
                                     INTEL_PASID_TEARDOWN_DRAIN_PRQ);

> +	domain_remove_dev_pasid(domain, dev, pasid);
>   }
>   
> -static int intel_iommu_set_dev_pasid(struct iommu_domain *domain,
> -				     struct device *dev, ioasid_t pasid,
> -				     struct iommu_domain *old)
> +static struct dev_pasid_info *
> +domain_prepare_dev_pasid(struct iommu_domain *domain,
> +			 struct device *dev, ioasid_t pasid)

Why do you want to return a struct pointer instead of an integer? The
returned pointer is not used after it is returned.

Also, how about renaming this helper to domain_add_dev_pasid() to pair
it with domain_remove_dev_pasid()?

>   {
>   	struct device_domain_info *info = dev_iommu_priv_get(dev);
>   	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> @@ -4293,22 +4299,13 @@ static int intel_iommu_set_dev_pasid(struct iommu_domain *domain,
>   	unsigned long flags;
>   	int ret;
>   
> -	if (!pasid_supported(iommu) || dev_is_real_dma_subdevice(dev))
> -		return -EOPNOTSUPP;
> -
> -	if (domain->dirty_ops)
> -		return -EINVAL;
> -
> -	if (context_copied(iommu, info->bus, info->devfn))
> -		return -EBUSY;
> -
>   	ret = prepare_domain_attach_device(domain, dev);
>   	if (ret)
> -		return ret;
> +		return ERR_PTR(ret);
>   
>   	dev_pasid = kzalloc(sizeof(*dev_pasid), GFP_KERNEL);
>   	if (!dev_pasid)
> -		return -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
>   
>   	ret = domain_attach_iommu(dmar_domain, iommu);
>   	if (ret)

Thanks,
baolu