linux-kernel - [PATCH v4 1/2] iommu/io-pgtable-arm: Add way to debug pgtable walk

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Date: Thu, 23 May 2024 10:52:21 -0700
From: Rob Clark <robdclark@...il.com>
To: dri-devel@...ts.freedesktop.org
Cc: linux-arm-msm@...r.kernel.org,
	freedreno@...ts.freedesktop.org,
	Will Deacon <will@...nel.org>,
	Rob Clark <robdclark@...omium.org>,
	Robin Murphy <robin.murphy@....com>,
	Joerg Roedel <joro@...tes.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Joao Martins <joao.m.martins@...cle.com>,
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM SMMU DRIVERS),
	iommu@...ts.linux.dev (open list:IOMMU SUBSYSTEM),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v4 1/2] iommu/io-pgtable-arm: Add way to debug pgtable walk

From: Rob Clark <robdclark@...omium.org>

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

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/iommu/io-pgtable-arm.c | 51 ++++++++++++++++++++++++++++------
 include/linux/io-pgtable.h     |  4 +++
 2 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index f7828a7aad41..f47a0e64bb35 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -693,17 +693,19 @@ 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,
+			int (*cb)(void *cb_data, void *pte, int level),
+			void *cb_data)
 {
 	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
 	arm_lpae_iopte pte, *ptep = data->pgd;
 	int lvl = data->start_level;
+	int ret;
 
 	do {
 		/* Valid IOPTE pointer? */
 		if (!ptep)
-			return 0;
+			return -EFAULT;
 
 		/* Grab the IOPTE we're interested in */
 		ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
@@ -711,22 +713,52 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
 
 		/* Valid entry? */
 		if (!pte)
-			return 0;
+			return -EFAULT;
+
+		ret = cb(cb_data, &pte, lvl);
+		if (ret)
+			return ret;
 
-		/* Leaf entry? */
+		/* Leaf entry?  If so, we've found the translation */
 		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 -EFAULT;
+}
+
+struct iova_to_phys_walk_data {
+	arm_lpae_iopte pte;
+	int level;
+};
+
+static int iova_to_phys_walk_cb(void *cb_data, void *pte, int level)
+{
+	struct iova_to_phys_walk_data *d = cb_data;
+
+	d->pte = *(arm_lpae_iopte *)pte;
+	d->level = level;
+
 	return 0;
+}
+
+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);
+	struct iova_to_phys_walk_data d;
+	int ret;
+
+	ret = arm_lpae_pgtable_walk(ops, iova, iova_to_phys_walk_cb, &d);
+	if (ret)
+		return 0;
 
-found_translation:
-	iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
-	return iopte_to_paddr(pte, data) | iova;
+	iova &= (ARM_LPAE_BLOCK_SIZE(d.level, data) - 1);
+	return iopte_to_paddr(d.pte, data) | iova;
 }
 
 static void arm_lpae_restrict_pgsizes(struct io_pgtable_cfg *cfg)
@@ -807,6 +839,7 @@ 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 86cf1f7ae389..261b48af068a 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -177,6 +177,7 @@ 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: (optional) Perform a page table walk for a given iova.
  *
  * These functions map directly onto the iommu_ops member functions with
  * the same names.
@@ -190,6 +191,9 @@ struct io_pgtable_ops {
 			      struct iommu_iotlb_gather *gather);
 	phys_addr_t (*iova_to_phys)(struct io_pgtable_ops *ops,
 				    unsigned long iova);
+	int (*pgtable_walk)(struct io_pgtable_ops *ops, unsigned long iova,
+			    int (*cb)(void *cb_data, void *pte, int level),
+			    void *cb_data);
 	int (*read_and_clear_dirty)(struct io_pgtable_ops *ops,
 				    unsigned long iova, size_t size,
 				    unsigned long flags,
-- 
2.45.1