Re: [PATCH v4 04/22] iommu: Add recoverable fault reporting

Jonathan Cameron
2019-06-18T15:44:27Z

On Sun, 9 Jun 2019 06:44:04 -0700
Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
>
> Some IOMMU hardware features, for example PCI's PRI and Arm SMMU's Stall,
> enable recoverable I/O page faults. Allow IOMMU drivers to report PRI Page
> Requests and Stall events through the new fault reporting API. The
> consumer of the fault can be either an I/O page fault handler in the host,
> or a guest OS.
>
> Once handled, the fault must be completed by sending a page response back
> to the IOMMU. Add an iommu_page_response() function to complete a page
> fault.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
One totally trivial ordering of docs comment in here. Otherwise good.

Jonathan
> ---
> drivers/iommu/iommu.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/iommu.h | 51 ++++++++++++++++++++++++++++++++++
> 2 files changed, 127 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 7955184..13b301c 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -869,7 +869,14 @@ EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> * @data: private data passed as argument to the handler
> *
> * When an IOMMU fault event is received, this handler gets called with the
> - * fault event and data as argument.
> + * fault event and data as argument. The handler should return 0 on success. If
> + * the fault is recoverable (IOMMU_FAULT_PAGE_REQ), the handler should also
> + * complete the fault by calling iommu_page_response() with one of the following
> + * response code:
> + * - IOMMU_PAGE_RESP_SUCCESS: retry the translation
> + * - IOMMU_PAGE_RESP_INVALID: terminate the fault
> + * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
> + * page faults if possible.
> *
> * Return 0 if the fault handler was installed successfully, or an error.
> */
> @@ -904,6 +911,8 @@ int iommu_register_device_fault_handler(struct device *dev,
> }
> param->fault_param->handler = handler;
> param->fault_param->data = data;
> + mutex_init(&param->fault_param->lock);
> + INIT_LIST_HEAD(&param->fault_param->faults);
>
> done_unlock:
> mutex_unlock(&param->lock);
> @@ -934,6 +943,12 @@ int iommu_unregister_device_fault_handler(struct device *dev)
> if (!param->fault_param)
> goto unlock;
>
> + /* we cannot unregister handler if there are pending faults */
> + if (!list_empty(&param->fault_param->faults)) {
> + ret = -EBUSY;
> + goto unlock;
> + }
> +
> kfree(param->fault_param);
> param->fault_param = NULL;
> put_device(dev);
> @@ -958,6 +973,7 @@ EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> {
> struct iommu_param *param = dev->iommu_param;
> + struct iommu_fault_event *evt_pending;
> struct iommu_fault_param *fparam;
> int ret = 0;
>
> @@ -972,6 +988,20 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> ret = -EINVAL;
> goto done_unlock;
> }
> +
> + if (evt->fault.type == IOMMU_FAULT_PAGE_REQ &&
> + (evt->fault.prm.flags & IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE)) {
> + evt_pending = kmemdup(evt, sizeof(struct iommu_fault_event),
> + GFP_KERNEL);
> + if (!evt_pending) {
> + ret = -ENOMEM;
> + goto done_unlock;
> + }
> + mutex_lock(&fparam->lock);
> + list_add_tail(&evt_pending->list, &fparam->faults);
> + mutex_unlock(&fparam->lock);
> + }
> +
> ret = fparam->handler(evt, fparam->data);
> done_unlock:
> mutex_unlock(&param->lock);
> @@ -1513,6 +1543,51 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
> }
> EXPORT_SYMBOL_GPL(iommu_attach_device);
>
> +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->fault.prm.pasid == msg->pasid &&
> + evt->fault.prm.grpid == msg->grpid) {
> + msg->iommu_data = evt->iommu_private;
> + ret = domain->ops->page_response(dev, msg);
> + list_del(&evt->list);
> + kfree(evt);
> + break;
> + }
> + }
> +
> +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 b87b74c..950347b 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -192,6 +192,42 @@ struct iommu_sva_ops {
> #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,
> +};
> +
> +/**
> + * struct page_response_msg - Generic page response information based on PCI ATS
> + * and PASID spec
> + * @addr: servicing page address
> + * @pasid: contains process address space ID
> + * @pasid_present: the @pasid field is valid
> + * @resp_code: response code
> + * @grpid: page request group index
> + * @iommu_data: data private to the IOMMU
> + */
> +struct page_response_msg {
> + u64 addr;
> + u32 pasid;
> + u32 pasid_present:1;
> + enum page_response_code resp_code;
> + u32 grpid;
> + u64 iommu_data;
> +};
> +
> +/**
> * struct iommu_ops - iommu ops and capabilities
> * @capable: check capability
> * @domain_alloc: allocate iommu domain
> @@ -227,6 +263,7 @@ struct iommu_sva_ops {
> * @sva_bind: Bind process address space to device
> * @sva_unbind: Unbind process address space from device
> * @sva_get_pasid: Get PASID associated to a SVA handle
> + * @page_response: handle page request response
> * @pgsize_bitmap: bitmap of all possible supported page sizes
> */
> struct iommu_ops {
> @@ -287,6 +324,8 @@ struct iommu_ops {
> void (*sva_unbind)(struct iommu_sva *handle);
> int (*sva_get_pasid)(struct iommu_sva *handle);
>
> + int (*page_response)(struct device *dev, struct page_response_msg *msg);
> +
> unsigned long pgsize_bitmap;
> };
>
> @@ -311,11 +350,13 @@ struct iommu_device {
> * unrecoverable faults such as DMA or IRQ remapping faults.
> *
> * @fault: fault descriptor
> + * @list: pending fault event list, used for tracking responses

Ordering of docs vs structure is wrong.

> * @iommu_private: used by the IOMMU driver for storing fault-specific
> * data. Users should not modify this field before
> * sending the fault response.
> */
> struct iommu_fault_event {
> + struct list_head list;
> struct iommu_fault fault;
> u64 iommu_private;
> };
> @@ -325,10 +366,14 @@ struct iommu_fault_event {
> *
> * @handler: Callback function to handle IOMMU faults at device level
> * @data: handler private data
> + * @faults: holds the pending faults which needs response, e.g. page response.
> + * @lock: protect pending faults list
> */
> struct iommu_fault_param {
> iommu_dev_fault_handler_t handler;
> void *data;
> + struct list_head faults;
> + struct mutex lock;
> };
>
> /**
> @@ -443,6 +488,7 @@ 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 *);
> @@ -770,6 +816,11 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> 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;