[PATCH v4 17/22] iommu/intel-svm: report device page request

[Jacob Pan]

If the source device of a page request has its PASID table pointer
bound to a guest, the first level page tables are owned by the guest.
In this case, we shall let guest OS to manage page fault.

This patch uses the IOMMU fault reporting API to send fault events,
possibly via VFIO, to the guest OS. Once guest pages are fault in, guest
will issue page response which will be passed down via the invalidation
passdown APIs.

Recoverable faults, such as page request reporting is not limitted to
guest use. In kernel driver can also request a chance to receive fault
notifications.

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
---
 drivers/iommu/intel-svm.c | 71 ++++++++++++++++++++++++++++++++++++++++-------
 include/linux/iommu.h     |  1 +
 2 files changed, 62 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 99bc9bd..bdc702c 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -580,6 +580,56 @@ static bool is_canonical_address(u64 addr)
 	return (((saddr << shift) >> shift) == saddr);
 }
 
+static int prq_to_iommu_prot(struct page_req_dsc *req)
+{
+	int prot = 0;
+
+	if (req->rd_req)
+		prot |= IOMMU_FAULT_READ;
+	if (req->wr_req)
+		prot |= IOMMU_FAULT_WRITE;
+	if (req->exe_req)
+		prot |= IOMMU_FAULT_EXEC;
+	if (req->priv_req)
+		prot |= IOMMU_FAULT_PRIV;
+
+	return prot;
+}
+
+static int intel_svm_prq_report(struct page_req_dsc *desc)
+{
+	int ret = 0;
+	struct iommu_fault_event event;
+	struct pci_dev *pdev;
+
+	memset(&event, 0, sizeof(struct iommu_fault_event));
+	pdev = pci_get_bus_and_slot(desc->bus, desc->devfn);
+	if (!pdev) {
+		pr_err("No PCI device found for PRQ [%02x:%02x.%d]\n",
+			desc->bus, PCI_SLOT(desc->devfn),
+			PCI_FUNC(desc->devfn));
+		return -ENODEV;
+	}
+
+	/* Fill in event data for device specific processing */
+	event.type = IOMMU_FAULT_PAGE_REQ;
+	event.addr = (u64)desc->addr << VTD_PAGE_SHIFT;
+	event.pasid = desc->pasid;
+	event.page_req_group_id = desc->prg_index;
+	event.prot = prq_to_iommu_prot(desc);
+	event.last_req = desc->lpig;
+	event.pasid_valid = 1;
+	/* keep track of PRQ so that when the response comes back, we know
+	 * whether we do group response or stream response. SRR[0] and
+	 * private[54:32] bits in the descriptor are stored.
+	 */
+	event.iommu_private = *(u64 *)desc;
+	ret = iommu_report_device_fault(&pdev->dev, &event);
+	pci_dev_put(pdev);
+
+	return ret;
+}
+
 static irqreturn_t prq_event_thread(int irq, void *d)
 {
 	struct intel_iommu *iommu = d;
@@ -628,6 +678,16 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 				goto no_pasid;
 			}
 		}
+		/* If address is not canonical, return invalid response */
+		if (!is_canonical_address(address))
+			goto bad_req;
+
+		/*
+		 * If prq is to be handled outside iommu driver via receiver of
+		 * the fault notifiers, we skip the page response here.
+		 */
+		if (!intel_svm_prq_report(req))
+			goto prq_advance;
 
 		result = QI_RESP_INVALID;
 		/* Since we're using init_mm.pgd directly, we should never take
@@ -638,9 +698,6 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 		if (!mmget_not_zero(svm->mm))
 			goto bad_req;
 
-		/* If address is not canonical, return invalid response */
-		if (!is_canonical_address(address))
-			goto bad_req;
 
 		down_read(&svm->mm->mmap_sem);
 		vma = find_extend_vma(svm->mm, address);
@@ -673,12 +730,6 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 
 		if (WARN_ON(&sdev->list == &svm->devs))
 			sdev = NULL;
-
-		if (sdev && sdev->ops && sdev->ops->fault_cb) {
-			int rwxp = (req->rd_req << 3) | (req->wr_req << 2) |
-				(req->exe_req << 1) | (req->priv_req);
-			sdev->ops->fault_cb(sdev->dev, req->pasid, req->addr, req->private, rwxp, result);
-		}
 		/* We get here in the error case where the PASID lookup failed,
 		   and these can be NULL. Do not use them below this point! */
 		sdev = NULL;
@@ -704,7 +755,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 
 			qi_submit_sync(&resp, iommu);
 		}
-
+	prq_advance:
 		head = (head + sizeof(*req)) & PRQ_RING_MASK;
 	}
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 94cfda8..dbe2866 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -42,6 +42,7 @@
  * if the IOMMU page table format is equivalent.
  */
 #define IOMMU_PRIV	(1 << 5)
+#define IOMMU_EXEC	(1 << 6)
 
 struct iommu_ops;
 struct iommu_group;
-- 
2.7.4