[PATCH v2 1/3] iommu/io-pgtable-arm: Add way to debug pgtable walk

Rob Clark
2021-10-05T15:12:02Z

From: Rob Clark <robdclark@chromium.org>

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>
---
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 dd9e47189d0d..c470fc0b3c2b 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -700,38 +700,61 @@ static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova,
return arm_lpae_unmap_pages(ops, iova, size, 1, gather);
}

-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;
}
@@ -816,6 +839,7 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
.unmap = arm_lpae_unmap,
.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 86af6f0a00a2..501f362a929c 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -148,6 +148,13 @@ struct io_pgtable_cfg {
* @unmap: Unmap a physically contiguous memory region.
* @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.
@@ -165,6 +172,8 @@ 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,
+ void *ptes, int *num_ptes);
};

/**
--
2.31.1