[PATCH v7 08/10] iommu: Prepare IOMMU domain for IOPF

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

This adds some mechanisms around the iommu_domain so that the I/O page
fault handling framework could route a page fault to the domain and
call the fault handler from it.

Add pointers to the page fault handler and its private data in struct
iommu_domain. The fault handler will be called with the private data
as a parameter once a page fault is routed to the domain. Any kernel
component which owns an iommu domain could install handler and its
private parameter so that the page fault could be further routed and
handled.

This also prepares the SVA implementation to be the first consumer of
the per-domain page fault handling model.

Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 include/linux/iommu.h         |  3 ++
 drivers/iommu/io-pgfault.c    |  7 ++++
 drivers/iommu/iommu-sva-lib.c | 65 +++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e4ce2fe0e144..45f274b2640d 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -100,6 +100,9 @@ struct iommu_domain {
 	void *handler_token;
 	struct iommu_domain_geometry geometry;
 	struct iommu_dma_cookie *iova_cookie;
+	enum iommu_page_response_code (*iopf_handler)(struct iommu_fault *fault,
+						      void *data);
+	void *fault_data;
 };
 
 static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
index 1df8c1dcae77..aee9e033012f 100644
--- a/drivers/iommu/io-pgfault.c
+++ b/drivers/iommu/io-pgfault.c
@@ -181,6 +181,13 @@ static void iopf_handle_group(struct work_struct *work)
  * request completes, outstanding faults will have been dealt with by the time
  * the PASID is freed.
  *
+ * Any valid page fault will be eventually routed to an iommu domain and the
+ * page fault handler installed there will get called. The users of this
+ * handling framework should guarantee that the iommu domain could only be
+ * freed after the device has stopped generating page faults (or the iommu
+ * hardware has been set to block the page faults) and the pending page faults
+ * have been flushed.
+ *
  * Return: 0 on success and <0 on error.
  */
 int iommu_queue_iopf(struct iommu_fault *fault, void *cookie)
diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
index 568e0f64edac..317ab8e8c149 100644
--- a/drivers/iommu/iommu-sva-lib.c
+++ b/drivers/iommu/iommu-sva-lib.c
@@ -72,6 +72,69 @@ struct mm_struct *iommu_sva_find(ioasid_t pasid)
 }
 EXPORT_SYMBOL_GPL(iommu_sva_find);
 
+/*
+ * I/O page fault handler for SVA
+ *
+ * Copied from io-pgfault.c with mmget_not_zero() added before
+ * mmap_read_lock().
+ */
+static enum iommu_page_response_code
+iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
+{
+	vm_fault_t ret;
+	struct mm_struct *mm;
+	struct vm_area_struct *vma;
+	unsigned int access_flags = 0;
+	struct iommu_domain *domain = data;
+	unsigned int fault_flags = FAULT_FLAG_REMOTE;
+	struct iommu_fault_page_request *prm = &fault->prm;
+	enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
+
+	if (!(prm->flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID))
+		return status;
+
+	mm = domain_to_mm(domain);
+	if (IS_ERR_OR_NULL(mm) || !mmget_not_zero(mm))
+		return status;
+
+	mmap_read_lock(mm);
+
+	vma = find_extend_vma(mm, prm->addr);
+	if (!vma)
+		/* Unmapped area */
+		goto out_put_mm;
+
+	if (prm->perm & IOMMU_FAULT_PERM_READ)
+		access_flags |= VM_READ;
+
+	if (prm->perm & IOMMU_FAULT_PERM_WRITE) {
+		access_flags |= VM_WRITE;
+		fault_flags |= FAULT_FLAG_WRITE;
+	}
+
+	if (prm->perm & IOMMU_FAULT_PERM_EXEC) {
+		access_flags |= VM_EXEC;
+		fault_flags |= FAULT_FLAG_INSTRUCTION;
+	}
+
+	if (!(prm->perm & IOMMU_FAULT_PERM_PRIV))
+		fault_flags |= FAULT_FLAG_USER;
+
+	if (access_flags & ~vma->vm_flags)
+		/* Access fault */
+		goto out_put_mm;
+
+	ret = handle_mm_fault(vma, prm->addr, fault_flags, NULL);
+	status = ret & VM_FAULT_ERROR ? IOMMU_PAGE_RESP_INVALID :
+		IOMMU_PAGE_RESP_SUCCESS;
+
+out_put_mm:
+	mmap_read_unlock(mm);
+	mmput(mm);
+
+	return status;
+}
+
 /*
  * IOMMU SVA driver-oriented interfaces
  */
@@ -94,6 +157,8 @@ iommu_sva_alloc_domain(struct bus_type *bus, struct mm_struct *mm)
 	domain = &sva_domain->domain;
 	domain->type = IOMMU_DOMAIN_SVA;
 	domain->ops = bus->iommu_ops->sva_domain_ops;
+	domain->iopf_handler = iommu_sva_handle_iopf;
+	domain->fault_data = domain;
 
 	return domain;
 }
-- 
2.25.1