Re: [PATCH v3 1/4] drivers/iommu: Add page_ext for IOMMU_DEBUG_PAGEALLOC
From: Baolu Lu
Date: Tue Nov 25 2025 - 02:23:17 EST
On 11/25/25 04:08, Mostafa Saleh wrote:
Add a new config IOMMU_DEBUG_PAGEALLOC, which registers new data to
page_ext.
This config will be used by the IOMMU API to track pages mapped in
the IOMMU to catch drivers trying to free kernel memory that they
still map in their domains, causing all types of memory corruption.
This behaviour is disabled by default and can be enabled using
kernel cmdline iommu.debug_pagealloc.
Signed-off-by: Mostafa Saleh <smostafa@xxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 6 ++++
drivers/iommu/Kconfig | 19 +++++++++++
drivers/iommu/Makefile | 1 +
drivers/iommu/iommu-debug-pagealloc.c | 32 +++++++++++++++++++
include/linux/iommu-debug-pagealloc.h | 17 ++++++++++
mm/page_ext.c | 4 +++
6 files changed, 79 insertions(+)
create mode 100644 drivers/iommu/iommu-debug-pagealloc.c
create mode 100644 include/linux/iommu-debug-pagealloc.h
[..]
diff --git a/include/linux/iommu-debug-pagealloc.h b/include/linux/iommu-debug-pagealloc.h
new file mode 100644
index 000000000000..83e64d70bf6c
--- /dev/null
+++ b/include/linux/iommu-debug-pagealloc.h
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 - Google Inc
+ * Author: Mostafa Saleh <smostafa@xxxxxxxxxx>
+ * IOMMU API debug page alloc sanitizer
+ */
+
+#ifndef __LINUX_IOMMU_DEBUG_PAGEALLOC_H
+#define __LINUX_IOMMU_DEBUG_PAGEALLOC_H
+
+#ifdef CONFIG_IOMMU_DEBUG_PAGEALLOC
+
+extern struct page_ext_operations page_iommu_debug_ops;
How about moving above to below mm/page_ext.c and remove iommu-debug-
pagealloc.h header file? ...
+
+#endif /* CONFIG_IOMMU_DEBUG_PAGEALLOC */
+
+#endif /* __LINUX_IOMMU_DEBUG_PAGEALLOC_H */
diff --git a/mm/page_ext.c b/mm/page_ext.c
index d7396a8970e5..297e4cd8ce90 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -11,6 +11,7 @@
#include <linux/page_table_check.h>
#include <linux/rcupdate.h>
#include <linux/pgalloc_tag.h>
+#include <linux/iommu-debug-pagealloc.h>
... remove this include line and put the "extern" line here,
extern struct page_ext_operations page_iommu_debug_ops;
/*
* struct page extension
@@ -89,6 +90,9 @@ static struct page_ext_operations *page_ext_ops[] __initdata = {
#ifdef CONFIG_PAGE_TABLE_CHECK
&page_table_check_ops,
#endif
+#ifdef CONFIG_IOMMU_DEBUG_PAGEALLOC
+ &page_iommu_debug_ops,
+#endif
};
unsigned long page_ext_size;
Or, put it directly in linux/iommu.h?
diff --git a/include/linux/iommu-debug-pagealloc.h
b/include/linux/iommu-debug-pagealloc.h
index 87f593305465..b2b82cf032e6 100644
--- a/include/linux/iommu-debug-pagealloc.h
+++ b/include/linux/iommu-debug-pagealloc.h
@@ -14,8 +14,6 @@ struct iommu_domain;
DECLARE_STATIC_KEY_FALSE(iommu_debug_initialized);
-extern struct page_ext_operations page_iommu_debug_ops;
-
void __iommu_debug_map(struct iommu_domain *domain, phys_addr_t phys,
size_t size);
void __iommu_debug_unmap_begin(struct iommu_domain *domain,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 801b2bd9e8d4..40133031985a 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1185,6 +1185,10 @@ void iommu_detach_device_pasid(struct
iommu_domain *domain,
struct device *dev, ioasid_t pasid);
ioasid_t iommu_alloc_global_pasid(struct device *dev);
void iommu_free_global_pasid(ioasid_t pasid);
+
+#ifdef CONFIG_IOMMU_DEBUG_PAGEALLOC
+extern struct page_ext_operations page_iommu_debug_ops;
+#endif /* CONFIG_IOMMU_DEBUG_PAGEALLOC */
#else /* CONFIG_IOMMU_API */
struct iommu_ops {};
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 297e4cd8ce90..345af8c9fcce 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -11,7 +11,7 @@
#include <linux/page_table_check.h>
#include <linux/rcupdate.h>
#include <linux/pgalloc_tag.h>
-#include <linux/iommu-debug-pagealloc.h>
+#include <linux/iommu.h>
/*
* struct page extension
Thanks,
baolu