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

Rob Clark
2024-05-23T17:52:33Z

From: Rob Clark <robdclark@chromium.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@chromium.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