[PATCH] iommu/vt-d: Make DMA-fault page-table dump user-selectable

[Ahmed Abdelraoof <araoof@amazon.de>]

From: Ahmed Abdelraoof <araoof@amazon.com>

The page-table dump was gated behind the hidden CONFIG_DMAR_DEBUG
symbol, only reachable by enabling the full INTEL_IOMMU_DEBUGFS
interface. That interface is explicitly flagged as not for production
and exposes far more IOMMU internals than a fault dump needs, so there
was no way to get this diagnostic from menuconfig on production kernel
without taking on the rest.

This patch renames it to CONFIG_DMAR_FAULT_DEBUG with a prompt and help
text so the fault dump can be enabled on its own, and updates all
references in iommu.c and dmar.h. INTEL_IOMMU_DEBUGFS still selects it,
so existing configs are unaffected; no functional change otherwise.

Signed-off-by: Ahmed Abdelraoof <araoof@amazon.com>
---
 drivers/iommu/intel/Kconfig | 11 ++++++++---
 drivers/iommu/intel/iommu.c |  2 +-
 include/linux/dmar.h        |  2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/intel/Kconfig b/drivers/iommu/intel/Kconfig
index 5471f814e073..59a05cefa728 100644
--- a/drivers/iommu/intel/Kconfig
+++ b/drivers/iommu/intel/Kconfig
@@ -6,8 +6,13 @@ config DMAR_TABLE
 config DMAR_PERF
 	bool
 
-config DMAR_DEBUG
-	bool
+config DMAR_FAULT_DEBUG
+	bool "Dump Intel IOMMU page tables on DMA fault"
+	depends on INTEL_IOMMU
+	help
+	  On a DMA Remapping (DMAR) fault, walk the Root / Context /
+	  PASID / second-level page-table entries for the faulting
+	  source-id and IOVA and emit them via pr_info.
 
 config INTEL_IOMMU
 	bool "Support for Intel IOMMU using DMA Remapping Devices"
@@ -39,7 +44,7 @@ config INTEL_IOMMU_DEBUGFS
 	bool "Export Intel IOMMU internals in Debugfs"
 	depends on IOMMU_DEBUGFS
 	select DMAR_PERF
-	select DMAR_DEBUG
+	select DMAR_FAULT_DEBUG
 	help
 	  !!!WARNING!!!
 
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 4d0e65bc131d..7c28ef700dda 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -549,7 +549,7 @@ static void free_context_table(struct intel_iommu *iommu)
 	iommu->root_entry = NULL;
 }
 
-#ifdef CONFIG_DMAR_DEBUG
+#ifdef CONFIG_DMAR_FAULT_DEBUG
 static void pgtable_walk(struct intel_iommu *iommu, unsigned long pfn,
 			 u8 bus, u8 devfn, struct dma_pte *parent, int level)
 {
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 692b2b445761..199cf01284fe 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -126,7 +126,7 @@ static inline int dmar_res_noop(struct acpi_dmar_header *hdr, void *arg)
 	return 0;
 }
 
-#ifdef CONFIG_DMAR_DEBUG
+#ifdef CONFIG_DMAR_FAULT_DEBUG
 void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id,
 			  unsigned long long addr, u32 pasid);
 #else
-- 
2.47.3




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