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@google.com>
---
.../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/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6c42061ca20e..dddf435a1c11 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2557,6 +2557,12 @@
1 - Bypass the IOMMU for DMA.
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
+ iommu.debug_pagealloc=
+ [KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this
+ parameter enables the feature at boot time. By default, it
+ is disabled and the system behave the same way as a kernel
+ built without CONFIG_IOMMU_DEBUG_PAGEALLOC.
+
io7= [HW] IO7 for Marvel-based Alpha systems
See comment before marvel_specify_io7 in
arch/alpha/kernel/core_marvel.c.
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 70d29b14d851..c9c1a1c1820e 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -383,4 +383,23 @@ config SPRD_IOMMU
Say Y here if you want to use the multimedia devices listed above.
+config IOMMU_DEBUG_PAGEALLOC
+ bool "Debug IOMMU mappings against page allocations"
+ depends on DEBUG_PAGEALLOC && IOMMU_API && PAGE_EXTENSION
+ help
+ This enables a consistency check between the kernel page allocator and
+ the IOMMU subsystem. It verifies that pages being allocated or freed
+ are not currently mapped in any IOMMU domain.
+
+ This helps detect DMA use-after-free bugs where a driver frees a page
+ but forgets to unmap it from the IOMMU, potentially allowing a device
+ to overwrite memory that the kernel has repurposed.
+
+ These checks are best-effort and may not detect all problems.
+
+ Due to performance overhead, this feature is disabled by default.
+ You must enable "iommu.debug_pagealloc" from the kernel command
+ line to activate the runtime checks.
+
+ If unsure, say N.
endif # IOMMU_SUPPORT
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 355294fa9033..8f5130b6a671 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -34,3 +34,4 @@ obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
obj-$(CONFIG_IOMMU_IOPF) += io-pgfault.o
obj-$(CONFIG_SPRD_IOMMU) += sprd-iommu.o
obj-$(CONFIG_APPLE_DART) += apple-dart.o
+obj-$(CONFIG_IOMMU_DEBUG_PAGEALLOC) += iommu-debug-pagealloc.o
diff --git a/drivers/iommu/iommu-debug-pagealloc.c b/drivers/iommu/iommu-debug-pagealloc.c
new file mode 100644
index 000000000000..4022e9af7f27
--- /dev/null
+++ b/drivers/iommu/iommu-debug-pagealloc.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 - Google Inc
+ * Author: Mostafa Saleh <smostafa@google.com>
+ * IOMMU API debug page alloc sanitizer
+ */
+#include <linux/atomic.h>
+#include <linux/iommu-debug-pagealloc.h>
+#include <linux/kernel.h>
+#include <linux/page_ext.h>
+
+static bool needed;
+
+struct iommu_debug_metadata {
+ atomic_t ref;
+};
+
+static __init bool need_iommu_debug(void)
+{
+ return needed;
+}
+
+struct page_ext_operations page_iommu_debug_ops = {
+ .size = sizeof(struct iommu_debug_metadata),
+ .need = need_iommu_debug,
+};
+
+static int __init iommu_debug_pagealloc(char *str)
+{
+ return kstrtobool(str, &needed);
+}
+early_param("iommu.debug_pagealloc", iommu_debug_pagealloc);
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@google.com>
+ * 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;
+
+#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>
/*
* 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;
--
2.52.0.460.gd25c4c69ec-googOn 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@google.com>
> ---
> .../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@google.com>
> + * 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
On Tue, Nov 25, 2025 at 03:17:47PM +0800, Baolu Lu wrote:
> 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@google.com>
> > ---
> > .../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@google.com>
> > + * 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;
This file is needed for other functions added later, which is then
included by iommu.c mm.h
Also, the pattern in page_ext looks that users have their own headers:
include/linux/page_owner.h:extern struct page_ext_operations page_owner_ops;
include/linux/page_table_check.h:extern struct page_ext_operations page_table_check_ops;
include/linux/pgalloc_tag.h:extern struct page_ext_operations page_alloc_tagging_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?
>
I tried that, but in the last patch we need to include that in linux/mm.h
which didn't compile and required including other files which seemed
unnecessary and that it would be better to isolate this feature.
Thanks,
Mostafa
> 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
On 11/24/25 12:08 PM, 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@google.com> > --- > .../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/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 6c42061ca20e..dddf435a1c11 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2557,6 +2557,12 @@ > 1 - Bypass the IOMMU for DMA. > unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. > > + iommu.debug_pagealloc= > + [KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this > + parameter enables the feature at boot time. By default, it > + is disabled and the system behave the same way as a kernel behaves > + built without CONFIG_IOMMU_DEBUG_PAGEALLOC. > + > io7= [HW] IO7 for Marvel-based Alpha systems > See comment before marvel_specify_io7 in > arch/alpha/kernel/core_marvel.c. -- ~Randy
I missed one other thing: On 11/24/25 3:13 PM, Randy Dunlap wrote: > > > On 11/24/25 12:08 PM, 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@google.com> >> --- >> .../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/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index 6c42061ca20e..dddf435a1c11 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -2557,6 +2557,12 @@ >> 1 - Bypass the IOMMU for DMA. >> unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. >> >> + iommu.debug_pagealloc= Please note what format the option parameter value takes and possible values, like iommu.passthrough above here in the kernel-parameters.txt file. >> + [KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this >> + parameter enables the feature at boot time. By default, it >> + is disabled and the system behave the same way as a kernel > > behaves > >> + built without CONFIG_IOMMU_DEBUG_PAGEALLOC. >> + >> io7= [HW] IO7 for Marvel-based Alpha systems >> See comment before marvel_specify_io7 in >> arch/alpha/kernel/core_marvel.c. > > -- ~Randy
On Mon, Nov 24, 2025 at 05:31:12PM -0800, Randy Dunlap wrote:
> I missed one other thing:
>
> On 11/24/25 3:13 PM, Randy Dunlap wrote:
> >
> >
> > On 11/24/25 12:08 PM, 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@google.com>
> >> ---
> >> .../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/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> >> index 6c42061ca20e..dddf435a1c11 100644
> >> --- a/Documentation/admin-guide/kernel-parameters.txt
> >> +++ b/Documentation/admin-guide/kernel-parameters.txt
> >> @@ -2557,6 +2557,12 @@
> >> 1 - Bypass the IOMMU for DMA.
> >> unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
> >>
> >> + iommu.debug_pagealloc=
>
> Please note what format the option parameter value takes and possible values,
> like iommu.passthrough above here in the kernel-parameters.txt file.
I see, I was following the kernel's “debug_pagealloc”. Although, the
implementation understands “={0,1}”, I can add something as:
Format: { "0" | "1" }
0 - Sanitizer disabled.
1 - Sanitizer enabled, expect run-time overhead.
To make it more clear.
Thanks,
Mostafa
>
> >> + [KNL,EARLY] When CONFIG_IOMMU_DEBUG_PAGEALLOC is set, this
> >> + parameter enables the feature at boot time. By default, it
> >> + is disabled and the system behave the same way as a kernel
> >
> > behaves
> >
> >> + built without CONFIG_IOMMU_DEBUG_PAGEALLOC.
> >> +
> >> io7= [HW] IO7 for Marvel-based Alpha systems
> >> See comment before marvel_specify_io7 in
> >> arch/alpha/kernel/core_marvel.c.
> >
> >
>
> --
> ~Randy
>
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