[PATCH v6 0/2] Base enablement of IOMMU debugfs support

[PATCH v6 0/2] Base enablement of IOMMU debugfs support

[Gary R Hook]

These patches create a top-level function, called at IOMMU initialization,
to create a debugfs directory for the IOMMU. Under this directory drivers
may create and populate-specific directories for their device internals.

Patch 1: general IOMMU enablement
Patch 2: basic AMD enablement to demonstrate linkage with patch 1

Introduce a new Kconfig parameter IOMMU_DEBUGFS to globally allow/disallow
debugfs code to be built.

The Makefile structure is intended to allow the use of a single switch for
turning on DebugFS.

Changes since v5:
 - Added parameters names in declarations/definitions
 - Reformatted an inline definition

Changes since v4:
 - Guard vendor-specific debugfs files in the Makefile
 - Call top-level routine from iommu_init()
 - Add function for instantiating a driver-specific directory
 - Change AMD driver code to use this new format

Changes since v3:
 - Remove superfluous calls to debugfs_initialized()
 - Emit a warning exactly one time
 - Change the Kconfig name to IOMMU_DEBUGFS
 - Change the way debugfs modules are made

Changes since v2:
 - Move a declaration to outside an ifdef
 - Remove a spurious blank line

Changes since v1:
 - Remove debug cruft
 - Remove cruft produced by design change
 - Change the lock to a mutex
 - Coding style fixes
 - Add a comment to document the framework

---

Gary R Hook (2):
      iommu - Enable debugfs exposure of IOMMU driver internals
      iommu/amd: Add basic debugfs infrastructure for AMD IOMMU


 drivers/iommu/Kconfig             |   11 ++++++
 drivers/iommu/Makefile            |    6 +++
 drivers/iommu/amd_iommu_debugfs.c |   39 +++++++++++++++++++++
 drivers/iommu/amd_iommu_init.c    |    6 ++-
 drivers/iommu/amd_iommu_proto.h   |    6 +++
 drivers/iommu/amd_iommu_types.h   |    3 ++
 drivers/iommu/iommu-debugfs.c     |   70 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/iommu.c             |    2 +
 include/linux/iommu.h             |   10 +++++
 9 files changed, 151 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/amd_iommu_debugfs.c
 create mode 100644 drivers/iommu/iommu-debugfs.c

--
Signature

[PATCH v6 1/2] iommu - Enable debugfs exposure of IOMMU driver internals

[Gary R Hook]

Provide base enablement for using debugfs to expose internal data of an
IOMMU driver. When called, create the /sys/kernel/debug/iommu directory.

Emit a strong warning at boot time to indicate that this feature is
enabled.

This function is called from iommu_init, and creates the initial DebugFS
directory. Drivers may then call iommu_debugfs_new_driver_dir() to
instantiate a device-specific directory to expose internal data.
It will return a pointer to the new dentry structure created in
/sys/kernel/debug/iommu, or NULL in the event of a failure.

Since the IOMMU driver can not be removed from the running system, there
is no need for an "off" function.

Signed-off-by: Gary R Hook <gary.hook@amd.com>
---
 drivers/iommu/Kconfig         |   11 ++++++
 drivers/iommu/Makefile        |    1 +
 drivers/iommu/iommu-debugfs.c |   70 +++++++++++++++++++++++++++++++++++++++++
 drivers/iommu/iommu.c         |    2 +
 include/linux/iommu.h         |   10 ++++++
 5 files changed, 94 insertions(+)
 create mode 100644 drivers/iommu/iommu-debugfs.c

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f3a21343e636..ff511fa8ca7d 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
 
 endmenu
 
+config IOMMU_DEBUGFS
+	bool "Export IOMMU internals in DebugFS"
+	depends on DEBUG_FS
+	default n
+	help
+	  Allows exposure of IOMMU device internals. This option enables
+	  the use of debugfs by IOMMU drivers as required. Devices can,
+	  at initialization time, cause the IOMMU code to create a top-level
+	  debug/iommu directory, and then populate a subdirectory with
+	  entries as required.
+
 config IOMMU_IOVA
 	tristate
 
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 1fb695854809..74cfbc392862 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_IOMMU_API) += iommu.o
 obj-$(CONFIG_IOMMU_API) += iommu-traces.o
 obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
+obj-$(CONFIG_IOMMU_DEBUGFS) += iommu-debugfs.o
 obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
diff --git a/drivers/iommu/iommu-debugfs.c b/drivers/iommu/iommu-debugfs.c
new file mode 100644
index 000000000000..9df3b44aef55
--- /dev/null
+++ b/drivers/iommu/iommu-debugfs.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IOMMU driver
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook@amd.com>
+ */
+
+#include <linux/pci.h>
+#include <linux/iommu.h>
+#include <linux/debugfs.h>
+
+static struct dentry *iommu_debugfs_dir;
+
+/**
+ * iommu_debugfs_setup - create the top-level iommu directory in debugfs
+ *
+ * Provide base enablement for using debugfs to expose internal data of an
+ * IOMMU driver. When called, this function creates the
+ * /sys/kernel/debug/iommu directory.
+ *
+ * Emit a strong warning at boot time to indicate that this feature is
+ * enabled.
+ *
+ * This function is called from iommu_init; drivers may then call
+ * iommu_debugfs_new_driver_dir() to instantiate a vendor-specific
+ * directory to be used to expose internal data.
+ */
+void iommu_debugfs_setup(void)
+{
+	if (!iommu_debugfs_dir) {
+		iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
+		if (iommu_debugfs_dir) {
+			pr_warn("\n");
+			pr_warn("*************************************************************\n");
+			pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
+			pr_warn("**                                                         **\n");
+			pr_warn("**  IOMMU DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL  **\n");
+			pr_warn("**                                                         **\n");
+			pr_warn("** This means that this kernel is built to expose internal **\n");
+			pr_warn("** IOMMU data structures, which may compromise security on **\n");
+			pr_warn("** your system.                                            **\n");
+			pr_warn("**                                                         **\n");
+			pr_warn("** If you see this message and you are not debugging the   **\n");
+			pr_warn("** kernel, report this immediately to your vendor!         **\n");
+			pr_warn("**                                                         **\n");
+			pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
+			pr_warn("*************************************************************\n");
+		}
+	}
+}
+
+/**
+ * iommu_debugfs_new_driver_dir - create a vendor directory under debugfs/iommu
+ * @vendor: name of the vendor-specific subdirectory to create
+ *
+ * This function is called by an IOMMU driver to create the top-level debugfs
+ * directory for that driver. The return value is the dentry for the requested
+ * vendor directory, or NULL in case of failure.
+ */
+struct dentry *iommu_debugfs_new_driver_dir(char *vendor)
+{
+	struct dentry *d_new;
+
+	d_new = debugfs_create_dir(vendor, iommu_debugfs_dir);
+
+	return d_new;
+}
+EXPORT_SYMBOL_GPL(iommu_debugfs_new_driver_dir);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d2aa23202bb9..350819f1c5e1 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1747,6 +1747,8 @@ static int __init iommu_init(void)
 					       NULL, kernel_kobj);
 	BUG_ON(!iommu_group_kset);
 
+	iommu_debugfs_setup();
+
 	return 0;
 }
 core_initcall(iommu_init);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 19938ee6eb31..25018ac0fdab 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -698,4 +698,14 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
 
 #endif /* CONFIG_IOMMU_API */
 
+#ifdef CONFIG_IOMMU_DEBUGFS
+void iommu_debugfs_setup(void);
+struct dentry *iommu_debugfs_new_driver_dir(char *vendor);
+#else
+static inline void iommu_debugfs_setup(void) {}
+static inline struct dentry *iommu_debugfs_new_driver_dir(char *vendor) { \
+	return NULL; \
+}
+#endif
+
 #endif /* __LINUX_IOMMU_H */

[PATCH v6 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU

[Gary R Hook]

Implement a skeleton framework for debugfs support in the
AMD IOMMU.


Signed-off-by: Gary R Hook <gary.hook@amd.com>
---
 drivers/iommu/Makefile            |    5 +++++
 drivers/iommu/amd_iommu_debugfs.c |   39 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/amd_iommu_init.c    |    6 ++++--
 drivers/iommu/amd_iommu_proto.h   |    6 ++++++
 drivers/iommu/amd_iommu_types.h   |    3 +++
 5 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/amd_iommu_debugfs.c

diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 74cfbc392862..dd980f7dd8b6 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -30,3 +30,8 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
 obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
 obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
+
+# This ensures that only the required files are compiled
+ifeq ($(CONFIG_IOMMU_DEBUGFS), y)
+obj-$(CONFIG_AMD_IOMMU) += amd_iommu_debugfs.o
+endif
diff --git a/drivers/iommu/amd_iommu_debugfs.c b/drivers/iommu/amd_iommu_debugfs.c
new file mode 100644
index 000000000000..6dff98552969
--- /dev/null
+++ b/drivers/iommu/amd_iommu_debugfs.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD IOMMU driver
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook@amd.com>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/iommu.h>
+#include <linux/pci.h>
+#include "amd_iommu_proto.h"
+#include "amd_iommu_types.h"
+
+static struct dentry *amd_iommu_debugfs;
+static DEFINE_MUTEX(amd_iommu_debugfs_lock);
+
+#define	MAX_NAME_LEN	20
+
+void amd_iommu_debugfs_setup(struct amd_iommu *iommu)
+{
+	char name[MAX_NAME_LEN + 1];
+
+	mutex_lock(&amd_iommu_debugfs_lock);
+	if (!amd_iommu_debugfs)
+		amd_iommu_debugfs = iommu_debugfs_new_driver_dir("amd");
+	mutex_unlock(&amd_iommu_debugfs_lock);
+
+	if (amd_iommu_debugfs) {
+		snprintf(name, MAX_NAME_LEN, "iommu%02d", iommu->index);
+		iommu->debugfs = debugfs_create_dir(name,
+						    amd_iommu_debugfs);
+		if (!iommu->debugfs) {
+			debugfs_remove_recursive(amd_iommu_debugfs);
+			amd_iommu_debugfs = NULL;
+		}
+	}
+}
diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 904c575d1677..031e6dbb8345 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -2721,6 +2721,7 @@ int __init amd_iommu_enable_faulting(void)
  */
 static int __init amd_iommu_init(void)
 {
+	struct amd_iommu *iommu;
 	int ret;
 
 	ret = iommu_go_to_state(IOMMU_INITIALIZED);
@@ -2730,14 +2731,15 @@ static int __init amd_iommu_init(void)
 			disable_iommus();
 			free_iommu_resources();
 		} else {
-			struct amd_iommu *iommu;
-
 			uninit_device_table_dma();
 			for_each_iommu(iommu)
 				iommu_flush_all_caches(iommu);
 		}
 	}
 
+	for_each_iommu(iommu)
+		amd_iommu_debugfs_setup(iommu);
+
 	return ret;
 }
 
diff --git a/drivers/iommu/amd_iommu_proto.h b/drivers/iommu/amd_iommu_proto.h
index 640c286a0ab9..39053f11dda3 100644
--- a/drivers/iommu/amd_iommu_proto.h
+++ b/drivers/iommu/amd_iommu_proto.h
@@ -33,6 +33,12 @@ extern void amd_iommu_uninit_devices(void);
 extern void amd_iommu_init_notifier(void);
 extern int amd_iommu_init_api(void);
 
+#ifdef CONFIG_IOMMU_DEBUGFS
+void amd_iommu_debugfs_setup(struct amd_iommu *iommu);
+#else
+static inline void amd_iommu_debugfs_setup(struct amd_iommu *iommu) {}
+#endif
+
 /* Needed for interrupt remapping */
 extern int amd_iommu_prepare(void);
 extern int amd_iommu_enable(void);
diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h
index 1c9b080276c9..2ca0959ae9e6 100644
--- a/drivers/iommu/amd_iommu_types.h
+++ b/drivers/iommu/amd_iommu_types.h
@@ -593,6 +593,9 @@ struct amd_iommu {
 
 	u32 flags;
 	volatile u64 __aligned(8) cmd_sem;
+
+	/* DebugFS Info */
+	struct dentry *debugfs;
 };
 
 static inline struct amd_iommu *dev_to_amd_iommu(struct device *dev)

Re: [PATCH v6 1/2] iommu - Enable debugfs exposure of IOMMU driver internals

[Robin Murphy]

Hi Gary,

Just a few trivial nitpicks below, otherwise:

Reviewed-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>

On 11/05/18 15:34, Gary R Hook wrote:
> Provide base enablement for using debugfs to expose internal data of an
> IOMMU driver. When called, create the /sys/kernel/debug/iommu directory.
> 
> Emit a strong warning at boot time to indicate that this feature is
> enabled.
> 
> This function is called from iommu_init, and creates the initial DebugFS
> directory. Drivers may then call iommu_debugfs_new_driver_dir() to
> instantiate a device-specific directory to expose internal data.
> It will return a pointer to the new dentry structure created in
> /sys/kernel/debug/iommu, or NULL in the event of a failure.
> 
> Since the IOMMU driver can not be removed from the running system, there
> is no need for an "off" function.
> 
> Signed-off-by: Gary R Hook <gary.hook-5C7GfCeVMHo@public.gmane.org>
> ---
>   drivers/iommu/Kconfig         |   11 ++++++
>   drivers/iommu/Makefile        |    1 +
>   drivers/iommu/iommu-debugfs.c |   70 +++++++++++++++++++++++++++++++++++++++++
>   drivers/iommu/iommu.c         |    2 +
>   include/linux/iommu.h         |   10 ++++++
>   5 files changed, 94 insertions(+)
>   create mode 100644 drivers/iommu/iommu-debugfs.c
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index f3a21343e636..ff511fa8ca7d 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
>   
>   endmenu
>   
> +config IOMMU_DEBUGFS
> +	bool "Export IOMMU internals in DebugFS"
> +	depends on DEBUG_FS
> +	default n

bool implicitly defaults to n anyway, so you don't really need to say it.

> +	help
> +	  Allows exposure of IOMMU device internals. This option enables
> +	  the use of debugfs by IOMMU drivers as required. Devices can,
> +	  at initialization time, cause the IOMMU code to create a top-level
> +	  debug/iommu directory, and then populate a subdirectory with
> +	  entries as required.
> +
>   config IOMMU_IOVA
>   	tristate
>   
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index 1fb695854809..74cfbc392862 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -2,6 +2,7 @@
>   obj-$(CONFIG_IOMMU_API) += iommu.o
>   obj-$(CONFIG_IOMMU_API) += iommu-traces.o
>   obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
> +obj-$(CONFIG_IOMMU_DEBUGFS) += iommu-debugfs.o
>   obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
>   obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
>   obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
> diff --git a/drivers/iommu/iommu-debugfs.c b/drivers/iommu/iommu-debugfs.c
> new file mode 100644
> index 000000000000..9df3b44aef55
> --- /dev/null
> +++ b/drivers/iommu/iommu-debugfs.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * IOMMU driver

"driver"? ;) I'd have thought something like "IOMMU debugfs core 
infrastructure", but arguably it's self-evident enough that it doesn't 
necessarily need describing at all.

> + *
> + * Copyright (C) 2018 Advanced Micro Devices, Inc.
> + *
> + * Author: Gary R Hook <gary.hook-5C7GfCeVMHo@public.gmane.org>
> + */
> +
> +#include <linux/pci.h>
> +#include <linux/iommu.h>
> +#include <linux/debugfs.h>
> +
> +static struct dentry *iommu_debugfs_dir;
> +
> +/**
> + * iommu_debugfs_setup - create the top-level iommu directory in debugfs
> + *
> + * Provide base enablement for using debugfs to expose internal data of an
> + * IOMMU driver. When called, this function creates the
> + * /sys/kernel/debug/iommu directory.
> + *
> + * Emit a strong warning at boot time to indicate that this feature is
> + * enabled.
> + *
> + * This function is called from iommu_init; drivers may then call
> + * iommu_debugfs_new_driver_dir() to instantiate a vendor-specific
> + * directory to be used to expose internal data.
> + */
> +void iommu_debugfs_setup(void)
> +{
> +	if (!iommu_debugfs_dir) {
> +		iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
> +		if (iommu_debugfs_dir) {
> +			pr_warn("\n");
> +			pr_warn("*************************************************************\n");
> +			pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
> +			pr_warn("**                                                         **\n");
> +			pr_warn("**  IOMMU DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL  **\n");
> +			pr_warn("**                                                         **\n");
> +			pr_warn("** This means that this kernel is built to expose internal **\n");
> +			pr_warn("** IOMMU data structures, which may compromise security on **\n");
> +			pr_warn("** your system.                                            **\n");
> +			pr_warn("**                                                         **\n");
> +			pr_warn("** If you see this message and you are not debugging the   **\n");
> +			pr_warn("** kernel, report this immediately to your vendor!         **\n");
> +			pr_warn("**                                                         **\n");
> +			pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
> +			pr_warn("*************************************************************\n");
> +		}
> +	}
> +}
> +
> +/**
> + * iommu_debugfs_new_driver_dir - create a vendor directory under debugfs/iommu
> + * @vendor: name of the vendor-specific subdirectory to create
> + *
> + * This function is called by an IOMMU driver to create the top-level debugfs
> + * directory for that driver. The return value is the dentry for the requested
> + * vendor directory, or NULL in case of failure.

According to kernel-doc.rst, return values should be in a dedicated 
section (i.e. "Return: The dentry...") rather than as part of the 
function description.

> + */
> +struct dentry *iommu_debugfs_new_driver_dir(char *vendor)

const char *?

> +{
> +	struct dentry *d_new;
> +
> +	d_new = debugfs_create_dir(vendor, iommu_debugfs_dir);
> +
> +	return d_new;
> +}
> +EXPORT_SYMBOL_GPL(iommu_debugfs_new_driver_dir);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index d2aa23202bb9..350819f1c5e1 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1747,6 +1747,8 @@ static int __init iommu_init(void)
>   					       NULL, kernel_kobj);
>   	BUG_ON(!iommu_group_kset);
>   
> +	iommu_debugfs_setup();
> +
>   	return 0;
>   }
>   core_initcall(iommu_init);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 19938ee6eb31..25018ac0fdab 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -698,4 +698,14 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
>   
>   #endif /* CONFIG_IOMMU_API */
>   
> +#ifdef CONFIG_IOMMU_DEBUGFS
> +void iommu_debugfs_setup(void);
> +struct dentry *iommu_debugfs_new_driver_dir(char *vendor);
> +#else
> +static inline void iommu_debugfs_setup(void) {}
> +static inline struct dentry *iommu_debugfs_new_driver_dir(char *vendor) { \

Since this is a function, not a macro, it doesn't really need the line 
continuations.

Robin.

> +	return NULL; \
> +}
> +#endif
> +
>   #endif /* __LINUX_IOMMU_H */
> 
> _______________________________________________
> iommu mailing list
> iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 

Re: [PATCH v6 1/2] iommu - Enable debugfs exposure of IOMMU driver internals

[Gary R Hook]

On 05/11/2018 10:22 AM, Robin Murphy wrote:
> Hi Gary,
> 
> Just a few trivial nitpicks below, otherwise:
> 
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> 
> On 11/05/18 15:34, Gary R Hook wrote:
>> Provide base enablement for using debugfs to expose internal data of an
>> IOMMU driver. When called, create the /sys/kernel/debug/iommu directory.
>>
>> Emit a strong warning at boot time to indicate that this feature is
>> enabled.
>>
>> This function is called from iommu_init, and creates the initial DebugFS
>> directory. Drivers may then call iommu_debugfs_new_driver_dir() to
>> instantiate a device-specific directory to expose internal data.
>> It will return a pointer to the new dentry structure created in
>> /sys/kernel/debug/iommu, or NULL in the event of a failure.
>>
>> Since the IOMMU driver can not be removed from the running system, there
>> is no need for an "off" function.
>>
>> Signed-off-by: Gary R Hook <gary.hook@amd.com>
>> ---
>>   drivers/iommu/Kconfig         |   11 ++++++
>>   drivers/iommu/Makefile        |    1 +
>>   drivers/iommu/iommu-debugfs.c |   70 
>> +++++++++++++++++++++++++++++++++++++++++
>>   drivers/iommu/iommu.c         |    2 +
>>   include/linux/iommu.h         |   10 ++++++
>>   5 files changed, 94 insertions(+)
>>   create mode 100644 drivers/iommu/iommu-debugfs.c
>>
>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>> index f3a21343e636..ff511fa8ca7d 100644
>> --- a/drivers/iommu/Kconfig
>> +++ b/drivers/iommu/Kconfig
>> @@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
>>   endmenu
>> +config IOMMU_DEBUGFS
>> +    bool "Export IOMMU internals in DebugFS"
>> +    depends on DEBUG_FS
>> +    default n
> 
> bool implicitly defaults to n anyway, so you don't really need to say it.

Roger.

> 
>> +    help
>> +      Allows exposure of IOMMU device internals. This option enables
>> +      the use of debugfs by IOMMU drivers as required. Devices can,
>> +      at initialization time, cause the IOMMU code to create a top-level
>> +      debug/iommu directory, and then populate a subdirectory with
>> +      entries as required.
>> +
>>   config IOMMU_IOVA
>>       tristate
>> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
>> index 1fb695854809..74cfbc392862 100644
>> --- a/drivers/iommu/Makefile
>> +++ b/drivers/iommu/Makefile
>> @@ -2,6 +2,7 @@
>>   obj-$(CONFIG_IOMMU_API) += iommu.o
>>   obj-$(CONFIG_IOMMU_API) += iommu-traces.o
>>   obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
>> +obj-$(CONFIG_IOMMU_DEBUGFS) += iommu-debugfs.o
>>   obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
>>   obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
>>   obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
>> diff --git a/drivers/iommu/iommu-debugfs.c 
>> b/drivers/iommu/iommu-debugfs.c
>> new file mode 100644
>> index 000000000000..9df3b44aef55
>> --- /dev/null
>> +++ b/drivers/iommu/iommu-debugfs.c
>> @@ -0,0 +1,70 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * IOMMU driver
> 
> "driver"? ;) I'd have thought something like "IOMMU debugfs core 
> infrastructure", but arguably it's self-evident enough that it doesn't 
> necessarily need describing at all.

Changed to your suggestion

> 
>> + *
>> + * Copyright (C) 2018 Advanced Micro Devices, Inc.
>> + *
>> + * Author: Gary R Hook <gary.hook@amd.com>
>> + */
>> +
>> +#include <linux/pci.h>
>> +#include <linux/iommu.h>
>> +#include <linux/debugfs.h>
>> +
>> +static struct dentry *iommu_debugfs_dir;
>> +
>> +/**
>> + * iommu_debugfs_setup - create the top-level iommu directory in debugfs
>> + *
>> + * Provide base enablement for using debugfs to expose internal data 
>> of an
>> + * IOMMU driver. When called, this function creates the
>> + * /sys/kernel/debug/iommu directory.
>> + *
>> + * Emit a strong warning at boot time to indicate that this feature is
>> + * enabled.
>> + *
>> + * This function is called from iommu_init; drivers may then call
>> + * iommu_debugfs_new_driver_dir() to instantiate a vendor-specific
>> + * directory to be used to expose internal data.
>> + */
>> +void iommu_debugfs_setup(void)
>> +{
>> +    if (!iommu_debugfs_dir) {
>> +        iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
>> +        if (iommu_debugfs_dir) {
>> +            pr_warn("\n");
>> +            
>> pr_warn("*************************************************************\n"); 
>>
>> +            pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE 
>> NOTICE    **\n");
>> +            
>> pr_warn("**                                                         
>> **\n");
>> +            pr_warn("**  IOMMU DebugFS SUPPORT HAS BEEN ENABLED IN 
>> THIS KERNEL  **\n");
>> +            
>> pr_warn("**                                                         
>> **\n");
>> +            pr_warn("** This means that this kernel is built to 
>> expose internal **\n");
>> +            pr_warn("** IOMMU data structures, which may compromise 
>> security on **\n");
>> +            pr_warn("** your 
>> system.                                            **\n");
>> +            
>> pr_warn("**                                                         
>> **\n");
>> +            pr_warn("** If you see this message and you are not 
>> debugging the   **\n");
>> +            pr_warn("** kernel, report this immediately to your 
>> vendor!         **\n");
>> +            
>> pr_warn("**                                                         
>> **\n");
>> +            pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE 
>> NOTICE    **\n");
>> +            
>> pr_warn("*************************************************************\n"); 
>>
>> +        }
>> +    }
>> +}
>> +
>> +/**
>> + * iommu_debugfs_new_driver_dir - create a vendor directory under 
>> debugfs/iommu
>> + * @vendor: name of the vendor-specific subdirectory to create
>> + *
>> + * This function is called by an IOMMU driver to create the top-level 
>> debugfs
>> + * directory for that driver. The return value is the dentry for the 
>> requested
>> + * vendor directory, or NULL in case of failure.
> 
> According to kernel-doc.rst, return values should be in a dedicated 
> section (i.e. "Return: The dentry...") rather than as part of the 
> function description.

A style change that happened along the way; my model was apparently 
older code. I've adjusted for this new style.

> 
>> + */
>> +struct dentry *iommu_debugfs_new_driver_dir(char *vendor)
> 
> const char *?

Sure thing.

> 
>> +{
>> +    struct dentry *d_new;
>> +
>> +    d_new = debugfs_create_dir(vendor, iommu_debugfs_dir);
>> +
>> +    return d_new;
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_debugfs_new_driver_dir);
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index d2aa23202bb9..350819f1c5e1 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1747,6 +1747,8 @@ static int __init iommu_init(void)
>>                              NULL, kernel_kobj);
>>       BUG_ON(!iommu_group_kset);
>> +    iommu_debugfs_setup();
>> +
>>       return 0;
>>   }
>>   core_initcall(iommu_init);
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 19938ee6eb31..25018ac0fdab 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -698,4 +698,14 @@ const struct iommu_ops 
>> *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
>>   #endif /* CONFIG_IOMMU_API */
>> +#ifdef CONFIG_IOMMU_DEBUGFS
>> +void iommu_debugfs_setup(void);
>> +struct dentry *iommu_debugfs_new_driver_dir(char *vendor);
>> +#else
>> +static inline void iommu_debugfs_setup(void) {}
>> +static inline struct dentry *iommu_debugfs_new_driver_dir(char 
>> *vendor) { \
> 
> Since this is a function, not a macro, it doesn't really need the line 
> continuations.

Yep. Done. And moved the curly brace to the next line.

> 
> Robin.
> 
>> +    return NULL; \
>> +}
>> +#endif
>> +
>>   #endif /* __LINUX_IOMMU_H */
>>
>> _______________________________________________
>> iommu mailing list
>> iommu@lists.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>>

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu