48d6e2ad630da362acbee06c498f11073da597df82ef8ab3ba972dc1.patch

From a80774a7a81f431ca6b0a39b100acd803c5e3cd4 Mon Sep 17 00:00:00 2001
From: Rob Clark <robdclark@chromium.org>
Date: Wed, 22 Sep 2021 15:30:21 -0700
Subject: [PATCH] FROMLIST: iommu/io-pgtable-arm: Add way to debug pgtable walk

Add an io-pgtable method to retrieve the raw PTEs that would be
traversed for a given iova access.

Signed-off-by: Rob Clark <robdclark@chromium.org>
(am from https://patchwork.freedesktop.org/patch/455308/)
(also found at https://lore.kernel.org/r/20210922223029.495772-2-robdclark@gmail.com)

BUG=b:201293781
TEST=boot coachz

Change-Id: I4186dd89942c3c2c8635e4102104e6e2b99e8a37
Disallow-Recycled-Builds: test-failures
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3251518
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Tested-by: Rob Clark <robdclark@chromium.org>
Auto-Submit: Rob Clark <robdclark@chromium.org>
Commit-Queue: Kristian H. Kristensen <hoegsberg@chromium.org>
---
 drivers/iommu/io-pgtable-arm.c | 40 +++++++++++++++++++++++++++-------
 include/linux/io-pgtable.h     |  9 ++++++++
 2 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 72dcdd468cf30d6ec32eaf0795463549076309b0..4ff8c11b1847d45ad685f2e278f5555d44e7cb66 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -675,38 +675,61 @@ static size_t arm_lpae_unmap_pages(struct io_pgtable_ops *ops, unsigned long iov
 				data->start_level, ptep);
 }
 
-static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
-					 unsigned long iova)
+static int arm_lpae_pgtable_walk(struct io_pgtable_ops *ops, unsigned long iova,
+				 void *_ptes, int *num_ptes)
 {
 	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
 	arm_lpae_iopte pte, *ptep = data->pgd;
+	arm_lpae_iopte *ptes = _ptes;
+	int max_ptes = *num_ptes;
 	int lvl = data->start_level;
 
+	*num_ptes = 0;
+
 	do {
+		if (*num_ptes >= max_ptes)
+			return -ENOSPC;
+
 		/* Valid IOPTE pointer? */
 		if (!ptep)
-			return 0;
+			return -EFAULT;
 
 		/* Grab the IOPTE we're interested in */
 		ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
 		pte = READ_ONCE(*ptep);
 
+		ptes[(*num_ptes)++] = pte;
+
 		/* Valid entry? */
 		if (!pte)
-			return 0;
+			return -EFAULT;
 
 		/* Leaf entry? */
 		if (iopte_leaf(pte, lvl, data->iop.fmt))
-			goto found_translation;
+			return 0;
 
 		/* Take it to the next level */
 		ptep = iopte_deref(pte, data);
 	} while (++lvl < ARM_LPAE_MAX_LEVELS);
 
-	/* Ran out of page tables to walk */
-	return 0;
+	return -EFAULT;
+}
+
+static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
+					 unsigned long iova)
+{
+	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
+	arm_lpae_iopte pte, ptes[ARM_LPAE_MAX_LEVELS];
+	int lvl, num_ptes = ARM_LPAE_MAX_LEVELS;
+	int ret;
+
+	ret = arm_lpae_pgtable_walk(ops, iova, ptes, &num_ptes);
+	if (ret)
+		return 0;
+
+	pte = ptes[num_ptes - 1];
+	lvl = num_ptes - 1 + data->start_level;
 
-found_translation:
 	iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
 	return iopte_to_paddr(pte, data) | iova;
 }
@@ -789,6 +812,7 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
 		.map_pages	= arm_lpae_map_pages,
 		.unmap_pages	= arm_lpae_unmap_pages,
 		.iova_to_phys	= arm_lpae_iova_to_phys,
+		.pgtable_walk	= arm_lpae_pgtable_walk,
 	};
 
 	return data;
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index 25142a0e2fc2c51d4c7807a1fb87cc21b16a163b..103d1640098400a217c3f308fe30b26c55ef6b32 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -153,6 +153,13 @@ struct io_pgtable_cfg {
  * @map_pages:    Map a physically contiguous range of pages of the same size.
  * @unmap_pages:  Unmap a range of virtually contiguous pages of the same size.
  * @iova_to_phys: Translate iova to physical address.
+ * @pgtable_walk: Return details of a page table walk for a given iova.
+ *                This returns the array of PTEs in a format that is
+ *                specific to the page table format.  The number of
+ *                PTEs can be format specific.  The num_ptes parameter
+ *                on input specifies the size of the ptes array, and
+ *                on output the number of PTEs filled in (which depends
+ *                on the number of PTEs walked to resolve the iova)
  *
  * These functions map directly onto the iommu_ops member functions with
  * the same names.
@@ -170,6 +177,8 @@ struct io_pgtable_ops {
 				    unsigned long iova, size_t size,
 				    unsigned long flags,
 				    struct iommu_dirty_bitmap *dirty);
+	int (*pgtable_walk)(struct io_pgtable_ops *ops, unsigned long iova,
+			    void *ptes, int *num_ptes);
 };
 
 /**
-- 
2.43.0.rc2.451.g8631bc7472-goog