Re: [PATCH v5 14/23] iommu: introduce page response function

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

Hi,

On 05/12/2018 04:54 AM, Jacob Pan wrote:
> IO page faults can be handled outside IOMMU subsystem. For an example,
> when nested translation is turned on and guest owns the
> first level page tables, device page request can be forwared
> to the guest for handling faults. As the page response returns
> by the guest, IOMMU driver on the host need to process the
> response which informs the device and completes the page request
> transaction.
>
> This patch introduces generic API function for page response
> passing from the guest or other in-kernel users. The definitions of
> the generic data is based on PCI ATS specification not limited to
> any vendor.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Link: https://lkml.org/lkml/2017/12/7/1725
> ---
>  drivers/iommu/iommu.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iommu.h | 43 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 88 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index b3f9daf..02fed3e 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1533,6 +1533,51 @@ int iommu_sva_invalidate(struct iommu_domain *domain,
>  }
>  EXPORT_SYMBOL_GPL(iommu_sva_invalidate);
>  
> +int iommu_page_response(struct device *dev,
> +			struct page_response_msg *msg)
> +{
> +	struct iommu_param *param = dev->iommu_param;
> +	int ret = -EINVAL;
> +	struct iommu_fault_event *evt;
> +	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> +
> +	if (!domain || !domain->ops->page_response)
> +		return -ENODEV;
> +
> +	/*
> +	 * Device iommu_param should have been allocated when device is
> +	 * added to its iommu_group.
> +	 */
> +	if (!param || !param->fault_param)
> +		return -EINVAL;
> +
> +	/* Only send response if there is a fault report pending */
> +	mutex_lock(&param->fault_param->lock);
> +	if (list_empty(&param->fault_param->faults)) {
> +		pr_warn("no pending PRQ, drop response\n");
> +		goto done_unlock;
> +	}
> +	/*
> +	 * Check if we have a matching page request pending to respond,
> +	 * otherwise return -EINVAL
> +	 */
> +	list_for_each_entry(evt, &param->fault_param->faults, list) {
> +		if (evt->pasid == msg->pasid &&
> +		    msg->page_req_group_id == evt->page_req_group_id) {
> +			msg->private_data = evt->iommu_private;
> +			ret = domain->ops->page_response(dev, msg);
> +			list_del(&evt->list);
> +			kfree(evt);
> +			break;
> +		}
> +	}

Are above two checks duplicated? We won't find a matching
request if the list is empty. And we need to  printk a message
if we can't find the matching request.

Best regards,
Lu Baolu

> +
> +done_unlock:
> +	mutex_unlock(&param->fault_param->lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_page_response);
> +
>  static void __iommu_detach_device(struct iommu_domain *domain,
>  				  struct device *dev)
>  {
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index b3312ee..722b90f 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -163,6 +163,41 @@ struct iommu_resv_region {
>  #ifdef CONFIG_IOMMU_API
>  
>  /**
> + * enum page_response_code - Return status of fault handlers, telling the IOMMU
> + * driver how to proceed with the fault.
> + *
> + * @IOMMU_PAGE_RESP_SUCCESS: Fault has been handled and the page tables
> + *	populated, retry the access. This is "Success" in PCI PRI.
> + * @IOMMU_PAGE_RESP_FAILURE: General error. Drop all subsequent faults from
> + *	this device if possible. This is "Response Failure" in PCI PRI.
> + * @IOMMU_PAGE_RESP_INVALID: Could not handle this fault, don't retry the
> + *	access. This is "Invalid Request" in PCI PRI.
> + */
> +enum page_response_code {
> +	IOMMU_PAGE_RESP_SUCCESS = 0,
> +	IOMMU_PAGE_RESP_INVALID,
> +	IOMMU_PAGE_RESP_FAILURE,
> +};
> +
> +/**
> + * Generic page response information based on PCI ATS and PASID spec.
> + * @addr: servicing page address
> + * @pasid: contains process address space ID
> + * @resp_code: response code
> + * @page_req_group_id: page request group index
> + * @private_data: uniquely identify device-specific private data for an
> + *                individual page response
> + */
> +struct page_response_msg {
> +	u64 addr;
> +	u32 pasid;
> +	enum page_response_code resp_code;
> +	u32 pasid_present:1;
> +	u32 page_req_group_id;
> +	u64 private_data;
> +};
> +
> +/**
>   * struct iommu_ops - iommu ops and capabilities
>   * @capable: check capability
>   * @domain_alloc: allocate iommu domain
> @@ -195,6 +230,7 @@ struct iommu_resv_region {
>   * @bind_pasid_table: bind pasid table pointer for guest SVM
>   * @unbind_pasid_table: unbind pasid table pointer and restore defaults
>   * @sva_invalidate: invalidate translation caches of shared virtual address
> + * @page_response: handle page request response
>   */
>  struct iommu_ops {
>  	bool (*capable)(enum iommu_cap);
> @@ -250,6 +286,7 @@ struct iommu_ops {
>  				struct device *dev);
>  	int (*sva_invalidate)(struct iommu_domain *domain,
>  		struct device *dev, struct tlb_invalidate_info *inv_info);
> +	int (*page_response)(struct device *dev, struct page_response_msg *msg);
>  
>  	unsigned long pgsize_bitmap;
>  };
> @@ -470,6 +507,7 @@ extern int iommu_unregister_device_fault_handler(struct device *dev);
>  
>  extern int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt);
>  
> +extern int iommu_page_response(struct device *dev, struct page_response_msg *msg);
>  extern int iommu_group_id(struct iommu_group *group);
>  extern struct iommu_group *iommu_group_get_for_dev(struct device *dev);
>  extern struct iommu_domain *iommu_group_default_domain(struct iommu_group *);
> @@ -758,6 +796,11 @@ static inline int iommu_report_device_fault(struct device *dev, struct iommu_fau
>  	return -ENODEV;
>  }
>  
> +static inline int iommu_page_response(struct device *dev, struct page_response_msg *msg)
> +{
> +	return -ENODEV;
> +}
> +
>  static inline int iommu_group_id(struct iommu_group *group)
>  {
>  	return -ENODEV;