[PATCH v4 0/2] Base enablement of IOMMU debugfs support

[PATCH v4 0/2] Base enablement of IOMMU debugfs support

[Gary R Hook]

These patches create a top-level function to create a debugfs directory
for the IOMMU, under which 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_DEBUG to globally allow or
disallow debugfs code to be built.

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 the IOMMU
      iommu/amd: Add basic debugfs infrastructure for AMD IOMMU


 drivers/iommu/Kconfig             |   11 +++++++
 drivers/iommu/Makefile            |    6 ++++
 drivers/iommu/amd_iommu_debugfs.c |   42 ++++++++++++++++++++++++++++
 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     |   55 +++++++++++++++++++++++++++++++++++++
 include/linux/iommu.h             |    4 +++
 8 files changed, 131 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/amd_iommu_debugfs.c
 create mode 100644 drivers/iommu/iommu-debugfs.c

--

[PATCH v4 1/2] iommu - Enable debugfs exposure of the IOMMU

[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 patch adds a top-level function that will create the (above)
directory, under which a driver may create a hw-specific directory for
its use. The function

	iommu_debugfs_setup()

returns a pointer to the new dentry structure created for
/sys/kernel/debug/iommu, or NULL in the event of a failure. An IOMMU
driver should call this function first, and then create a directory
beneath it. A driver implementation might look something like:

static struct dentry *my_debugfs;

	struct dentry *d_top;
	if (!my_debugfs) {
		d_top = iommu_debugfs_setup();
		if (d_top)
			my_debugfs = debugfs_create_dir("vendor", d_top);
	}

Since the IOMMU driver can not be removed from the running system, this
patch only provides an "on" 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 |   55 +++++++++++++++++++++++++++++++++++++++++
 include/linux/iommu.h         |    4 +++
 4 files changed, 71 insertions(+)
 create mode 100644 drivers/iommu/iommu-debugfs.c

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f3a21343e636..81a6c281e69f 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
 
 endmenu
 
+config IOMMU_DEBUGFS
+	bool "Enable 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..409691ca0ff9
--- /dev/null
+++ b/drivers/iommu/iommu-debugfs.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IOMMU driver
+ *
+ * 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;
+
+/*
+ * 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 top-level function that will create the (above) directory, under a
+ * driver may create a hw-specific directory for its use. The function
+ *
+ *     iommu_debugfs_setup()
+ *
+ * returns a pointer to the new dentry structure created for
+ * /sys/kernel/debug/iommu, or NULL in the event of a failure. An IOMMU
+ * driver should call this function first, and then create a directory
+ * beneath it. A driver implementation might look something like:
+ *
+ * static struct dentry *my_debugfs;
+ *
+ *    struct dentry *d_top;
+ *    if (!my_debugfs) {
+ *        d_top = iommu_debugfs_setup();
+ *        if (d_top)
+ *            my_debugfs = debugfs_create_dir("vendor", d_top);
+ *    }
+ *
+ * Since the IOMMU driver can not be removed from the running system, there
+ * is no need for an "off" function.
+ */
+struct dentry *iommu_debugfs_setup(void)
+{
+	if (!iommu_debugfs_dir) {
+		iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
+		if (iommu_debugfs_dir)
+			pr_warn("WARNING: IOMMU DEBUGFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL\n");
+	}
+
+	return iommu_debugfs_dir;
+}
+EXPORT_SYMBOL_GPL(iommu_debugfs_setup);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 19938ee6eb31..e5657c70f90c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -698,4 +698,8 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
 
 #endif /* CONFIG_IOMMU_API */
 
+#ifdef CONFIG_IOMMU_DEBUGFS
+struct dentry *iommu_debugfs_setup(void);
+#endif
+
 #endif /* __LINUX_IOMMU_H */

Re: [PATCH v4 1/2] iommu - Enable debugfs exposure of the IOMMU

[Joerg Roedel]

On Mon, Apr 30, 2018 at 02:58:49PM -0500, 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 patch adds a top-level function that will create the (above)
> directory, under which a driver may create a hw-specific directory for
> its use. The function
> 
> 	iommu_debugfs_setup()

That function should be called in iommu core-code, in case we want to
export some generic information from there.

Each driver then calls a separate function like

	dentry = iommu_debugfs_driver_dir("amd_iommu");

to create a driver-specific directory.

> +config IOMMU_DEBUGFS
> +	bool "Enable IOMMU internals in DebugFS"

s/Enable/Export/

> + * static struct dentry *my_debugfs;
> + *
> + *    struct dentry *d_top;

Missing newline

> + *    if (!my_debugfs) {
> + *        d_top = iommu_debugfs_setup();
> + *        if (d_top)
> + *            my_debugfs = debugfs_create_dir("vendor", d_top);
> + *    }
> + *
> + * Since the IOMMU driver can not be removed from the running system, there
> + * is no need for an "off" function.
> + */
> +struct dentry *iommu_debugfs_setup(void)
> +{
> +	if (!iommu_debugfs_dir) {
> +		iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
> +		if (iommu_debugfs_dir)
> +			pr_warn("WARNING: IOMMU DEBUGFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL\n");

This warning needs to be a lot bigger. See the trace_printk() warning
for an example of what I have in mind.

[PATCH v4 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-5C7GfCeVMHo@public.gmane.org>
---
 drivers/iommu/Makefile            |    5 ++++
 drivers/iommu/amd_iommu_debugfs.c |   42 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/amd_iommu_init.c    |    6 ++++-
 drivers/iommu/amd_iommu_proto.h   |    6 +++++
 drivers/iommu/amd_iommu_types.h   |    3 +++
 5 files changed, 60 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..34bb65cbd798
--- /dev/null
+++ b/drivers/iommu/amd_iommu_debugfs.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD IOMMU driver
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook-5C7GfCeVMHo@public.gmane.org>
+ */
+
+#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];
+	struct dentry *d_top;
+
+	mutex_lock(&amd_iommu_debugfs_lock);
+	if (!amd_iommu_debugfs) {
+		d_top = iommu_debugfs_setup();
+		if (d_top)
+			amd_iommu_debugfs = debugfs_create_dir("amd", d_top);
+	}
+	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)