[PATCH v6 0/2] io-pgtable-arm + drm/msm: Extend iova fault debugging

[PATCH v6 0/2] io-pgtable-arm + drm/msm: Extend iova fault debugging

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

This series extends io-pgtable-arm with a method to retrieve the page
table entries traversed in the process of address translation, and then
beefs up drm/msm gpu devcore dump to include this (and additional info)
in the devcore dump.

This is a respin of https://patchwork.freedesktop.org/series/94968/
(minus a patch that was already merged)

v2: Fix an armv7/32b build error in the last patch
v3: Incorperate Will Deacon's suggestion to make the interface
    callback based.
v4: Actually wire up the callback
v5: Drop the callback approach
v6: Make walk-data struct pgtable specific and rename
    io_pgtable_walk_data to arm_lpae_io_pgtable_walk_data

Rob Clark (2):
  iommu/io-pgtable-arm: Add way to debug pgtable walk
  drm/msm: Extend gpu devcore dumps with pgtbl info

 drivers/gpu/drm/msm/adreno/adreno_gpu.c | 10 +++++++
 drivers/gpu/drm/msm/msm_gpu.c           |  9 +++++++
 drivers/gpu/drm/msm/msm_gpu.h           |  8 ++++++
 drivers/gpu/drm/msm/msm_iommu.c         | 22 +++++++++++++++
 drivers/gpu/drm/msm/msm_mmu.h           |  3 ++-
 drivers/iommu/io-pgtable-arm.c          | 36 ++++++++++++++++++-------
 include/linux/io-pgtable.h              | 17 ++++++++++++
 7 files changed, 95 insertions(+), 10 deletions(-)

-- 
2.45.2

[PATCH v6 1/2] iommu/io-pgtable-arm: Add way to debug pgtable walk

[Rob Clark]

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>
Acked-by: Joerg Roedel <jroedel@suse.de>

---
 drivers/iommu/io-pgtable-arm.c | 36 +++++++++++++++++++++++++---------
 include/linux/io-pgtable.h     | 17 ++++++++++++++++
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 3d23b924cec1..e70803940b46 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -690,9 +690,11 @@ 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 *_wd)
 {
+	struct arm_lpae_io_pgtable_walk_data *wd = _wd;
 	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
 	arm_lpae_iopte pte, *ptep = data->pgd;
 	int lvl = data->start_level;
@@ -700,7 +702,7 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
 	do {
 		/* Valid IOPTE pointer? */
 		if (!ptep)
-			return 0;
+			return -ENOENT;
 
 		/* Grab the IOPTE we're interested in */
 		ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
@@ -708,22 +710,37 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
 
 		/* Valid entry? */
 		if (!pte)
-			return 0;
+			return -ENOENT;
 
-		/* Leaf entry? */
+		wd->ptes[wd->level++] = pte;
+
+		/* 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 0;
+	return -ENOENT;
+}
+
+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 arm_lpae_io_pgtable_walk_data wd = {};
+	int ret, lvl;
+
+	ret = arm_lpae_pgtable_walk(ops, iova, &wd);
+	if (ret)
+		return 0;
+
+	lvl = wd.level + data->start_level;
 
-found_translation:
 	iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
-	return iopte_to_paddr(pte, data) | iova;
+	return iopte_to_paddr(wd.ptes[wd.level - 1], data) | iova;
 }
 
 static void arm_lpae_restrict_pgsizes(struct io_pgtable_cfg *cfg)
@@ -804,6 +821,7 @@ 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..df6f6e58310c 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -171,12 +171,28 @@ struct io_pgtable_cfg {
 	};
 };
 
+/**
+ * struct arm_lpae_io_pgtable_walk_data - information from a pgtable walk
+ *
+ * @ptes:     The recorded PTE values from the walk
+ * @level:    The level of the last PTE
+ *
+ * @level also specifies the last valid index in @ptes
+ */
+struct arm_lpae_io_pgtable_walk_data {
+	u64 ptes[4];
+	int level;
+};
+
 /**
  * struct io_pgtable_ops - Page table manipulation API for IOMMU drivers.
  *
  * @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.  The
+ *                type for the wd parameter is specific to pgtable type, as
+ *                the PTE size and number of levels differs per pgtable type.
  *
  * These functions map directly onto the iommu_ops member functions with
  * the same names.
@@ -190,6 +206,7 @@ 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 *wd);
 	int (*read_and_clear_dirty)(struct io_pgtable_ops *ops,
 				    unsigned long iova, size_t size,
 				    unsigned long flags,
-- 
2.45.2

Re: [PATCH v6 1/2] iommu/io-pgtable-arm: Add way to debug pgtable walk

[Mostafa Saleh]

Hi Rob,

On Wed, Jul 17, 2024 at 09:36:21AM -0700, Rob Clark wrote:
> 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>
> Acked-by: Joerg Roedel <jroedel@suse.de>
> 
> ---
>  drivers/iommu/io-pgtable-arm.c | 36 +++++++++++++++++++++++++---------
>  include/linux/io-pgtable.h     | 17 ++++++++++++++++
>  2 files changed, 44 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 3d23b924cec1..e70803940b46 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -690,9 +690,11 @@ 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 *_wd)
>  {
> +	struct arm_lpae_io_pgtable_walk_data *wd = _wd;
>  	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
>  	arm_lpae_iopte pte, *ptep = data->pgd;
>  	int lvl = data->start_level;
> @@ -700,7 +702,7 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
>  	do {
>  		/* Valid IOPTE pointer? */
>  		if (!ptep)
> -			return 0;
> +			return -ENOENT;
>  
>  		/* Grab the IOPTE we're interested in */
>  		ptep += ARM_LPAE_LVL_IDX(iova, lvl, data);
> @@ -708,22 +710,37 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
>  
>  		/* Valid entry? */
>  		if (!pte)
> -			return 0;
> +			return -ENOENT;
>  
> -		/* Leaf entry? */
> +		wd->ptes[wd->level++] = pte;
> +
> +		/* 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 0;
> +	return -ENOENT;
> +}
> +
> +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 arm_lpae_io_pgtable_walk_data wd = {};
> +	int ret, lvl;
> +
> +	ret = arm_lpae_pgtable_walk(ops, iova, &wd);
> +	if (ret)
> +		return 0;
> +
> +	lvl = wd.level + data->start_level;
>  
> -found_translation:
>  	iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1);
> -	return iopte_to_paddr(pte, data) | iova;
> +	return iopte_to_paddr(wd.ptes[wd.level - 1], data) | iova;
>  }
>  
>  static void arm_lpae_restrict_pgsizes(struct io_pgtable_cfg *cfg)
> @@ -804,6 +821,7 @@ 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..df6f6e58310c 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -171,12 +171,28 @@ struct io_pgtable_cfg {
>  	};
>  };
>  
> +/**
> + * struct arm_lpae_io_pgtable_walk_data - information from a pgtable walk
> + *
> + * @ptes:     The recorded PTE values from the walk
> + * @level:    The level of the last PTE
> + *
> + * @level also specifies the last valid index in @ptes
> + */
> +struct arm_lpae_io_pgtable_walk_data {
> +	u64 ptes[4];

I don’t see a reason to save the whole walk for iova_to_phys,
I see that the DRM driver uses those next, but I am worried that
won’t scale, a callback mechanism sounds better.

Also, there is a page table walker recently added to io-pagtable-arm,
for dirty bit tracking:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/iommu/io-pgtable-arm.c?id=4fe88fd8b4aecb7f9680bf898811db76b94095a9

I’d suggest consolidating those into one walker where each caller
has its own logic in a callback.

Thanks,
Mostafa

> +	int level;
> +};
> +
>  /**
>   * struct io_pgtable_ops - Page table manipulation API for IOMMU drivers.
>   *
>   * @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.  The
> + *                type for the wd parameter is specific to pgtable type, as
> + *                the PTE size and number of levels differs per pgtable type.
>   *
>   * These functions map directly onto the iommu_ops member functions with
>   * the same names.
> @@ -190,6 +206,7 @@ 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 *wd);
>  	int (*read_and_clear_dirty)(struct io_pgtable_ops *ops,
>  				    unsigned long iova, size_t size,
>  				    unsigned long flags,
> -- 
> 2.45.2
> 

[PATCH v6 2/2] drm/msm: Extend gpu devcore dumps with pgtbl info

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

In the case of iova fault triggered devcore dumps, include additional
debug information based on what we think is the current page tables,
including the TTBR0 value (which should match what we have in
adreno_smmu_fault_info unless things have gone horribly wrong), and
the pagetable entries traversed in the process of resolving the
faulting iova.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/adreno/adreno_gpu.c | 10 ++++++++++
 drivers/gpu/drm/msm/msm_gpu.c           |  9 +++++++++
 drivers/gpu/drm/msm/msm_gpu.h           |  8 ++++++++
 drivers/gpu/drm/msm/msm_iommu.c         | 22 ++++++++++++++++++++++
 drivers/gpu/drm/msm/msm_mmu.h           |  3 ++-
 5 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index 99661af8d941..422dae873b6b 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -861,6 +861,16 @@ void adreno_show(struct msm_gpu *gpu, struct msm_gpu_state *state,
 		drm_printf(p, "  - dir=%s\n", info->flags & IOMMU_FAULT_WRITE ? "WRITE" : "READ");
 		drm_printf(p, "  - type=%s\n", info->type);
 		drm_printf(p, "  - source=%s\n", info->block);
+
+		/* Information extracted from what we think are the current
+		 * pgtables.  Hopefully the TTBR0 matches what we've extracted
+		 * from the SMMU registers in smmu_info!
+		 */
+		drm_puts(p, "pgtable-fault-info:\n");
+		drm_printf(p, "  - ttbr0: %.16llx\n", (u64)info->pgtbl_ttbr0);
+		drm_printf(p, "  - asid: %d\n", info->asid);
+		drm_printf(p, "  - ptes: %.16llx %.16llx %.16llx %.16llx\n",
+			   info->ptes[0], info->ptes[1], info->ptes[2], info->ptes[3]);
 	}
 
 	drm_printf(p, "rbbm-status: 0x%08x\n", state->rbbm_status);
diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 3666b42b4ecd..bf2f8b2a7ccc 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -281,6 +281,15 @@ static void msm_gpu_crashstate_capture(struct msm_gpu *gpu,
 	if (submit) {
 		int i;
 
+		if (state->fault_info.ttbr0) {
+			struct msm_gpu_fault_info *info = &state->fault_info;
+			struct msm_mmu *mmu = submit->aspace->mmu;
+
+			msm_iommu_pagetable_params(mmu, &info->pgtbl_ttbr0,
+						   &info->asid);
+			msm_iommu_pagetable_walk(mmu, info->iova, info->ptes);
+		}
+
 		state->bos = kcalloc(submit->nr_bos,
 			sizeof(struct msm_gpu_state_bo), GFP_KERNEL);
 
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 1f02bb9956be..82e838ba8c80 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -101,6 +101,14 @@ struct msm_gpu_fault_info {
 	int flags;
 	const char *type;
 	const char *block;
+
+	/* Information about what we think/expect is the current SMMU state,
+	 * for example expected_ttbr0 should match smmu_info.ttbr0 which
+	 * was read back from SMMU registers.
+	 */
+	phys_addr_t pgtbl_ttbr0;
+	u64 ptes[4];
+	int asid;
 };
 
 /**
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index d5512037c38b..0c35a5b597f3 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -195,6 +195,28 @@ struct iommu_domain_geometry *msm_iommu_get_geometry(struct msm_mmu *mmu)
 	return &iommu->domain->geometry;
 }
 
+int
+msm_iommu_pagetable_walk(struct msm_mmu *mmu, unsigned long iova, uint64_t ptes[4])
+{
+	struct msm_iommu_pagetable *pagetable;
+	struct arm_lpae_io_pgtable_walk_data wd = {};
+
+	if (mmu->type != MSM_MMU_IOMMU_PAGETABLE)
+		return -EINVAL;
+
+	pagetable = to_pagetable(mmu);
+
+	if (!pagetable->pgtbl_ops->pgtable_walk)
+		return -EINVAL;
+
+	pagetable->pgtbl_ops->pgtable_walk(pagetable->pgtbl_ops, iova, &wd);
+
+	for (int i = 0; i < ARRAY_SIZE(wd.ptes); i++)
+		ptes[i] = wd.ptes[i];
+
+	return 0;
+}
+
 static const struct msm_mmu_funcs pagetable_funcs = {
 		.map = msm_iommu_pagetable_map,
 		.unmap = msm_iommu_pagetable_unmap,
diff --git a/drivers/gpu/drm/msm/msm_mmu.h b/drivers/gpu/drm/msm/msm_mmu.h
index 88af4f490881..96e509bd96a6 100644
--- a/drivers/gpu/drm/msm/msm_mmu.h
+++ b/drivers/gpu/drm/msm/msm_mmu.h
@@ -53,7 +53,8 @@ static inline void msm_mmu_set_fault_handler(struct msm_mmu *mmu, void *arg,
 struct msm_mmu *msm_iommu_pagetable_create(struct msm_mmu *parent);
 
 int msm_iommu_pagetable_params(struct msm_mmu *mmu, phys_addr_t *ttbr,
-		int *asid);
+			       int *asid);
+int msm_iommu_pagetable_walk(struct msm_mmu *mmu, unsigned long iova, uint64_t ptes[4]);
 struct iommu_domain_geometry *msm_iommu_get_geometry(struct msm_mmu *mmu);
 
 #endif /* __MSM_MMU_H__ */
-- 
2.45.2

Re: [PATCH v6 2/2] drm/msm: Extend gpu devcore dumps with pgtbl info

[Konrad Dybcio]

On 17.07.2024 6:36 PM, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> In the case of iova fault triggered devcore dumps, include additional
> debug information based on what we think is the current page tables,
> including the TTBR0 value (which should match what we have in
> adreno_smmu_fault_info unless things have gone horribly wrong), and
> the pagetable entries traversed in the process of resolving the
> faulting iova.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 10 ++++++++++
>  drivers/gpu/drm/msm/msm_gpu.c           |  9 +++++++++
>  drivers/gpu/drm/msm/msm_gpu.h           |  8 ++++++++
>  drivers/gpu/drm/msm/msm_iommu.c         | 22 ++++++++++++++++++++++
>  drivers/gpu/drm/msm/msm_mmu.h           |  3 ++-
>  5 files changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index 99661af8d941..422dae873b6b 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -861,6 +861,16 @@ void adreno_show(struct msm_gpu *gpu, struct msm_gpu_state *state,
>  		drm_printf(p, "  - dir=%s\n", info->flags & IOMMU_FAULT_WRITE ? "WRITE" : "READ");
>  		drm_printf(p, "  - type=%s\n", info->type);
>  		drm_printf(p, "  - source=%s\n", info->block);
> +
> +		/* Information extracted from what we think are the current

I'll keep poking you for not using

/*
 * foobar

instead :P

> +		 * pgtables.  Hopefully the TTBR0 matches what we've extracted
> +		 * from the SMMU registers in smmu_info!
> +		 */
> +		drm_puts(p, "pgtable-fault-info:\n");
> +		drm_printf(p, "  - ttbr0: %.16llx\n", (u64)info->pgtbl_ttbr0);> +		drm_printf(p, "  - asid: %d\n", info->asid);

0x%08x?

Konrad