[PATCH v8 04/29] iommu: Add recoverable fault reporting

From: Eric Auger
Date: Sun May 26 2019 - 12:13:52 EST

From: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
---
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 795518445a3a..13b301cfb10f 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 b87b74c63cf9..950347be47f9 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -191,6 +191,42 @@ 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
@@ -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
* @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;
--
2.20.1