Re: [PATCH v8 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU
From: Gary R Hook
Date: Tue Jun 05 2018 - 12:58:28 EST
On 05/29/2018 01:39 PM, Greg KH wrote:
On Tue, May 29, 2018 at 01:23:23PM -0500, Gary R Hook wrote:
Implement a skeleton framework for debugfs support in the
AMD IOMMU. Add a hidden boolean to Kconfig that is defined
for the AMD IOMMU when general IOMMY DebugFS support is
enabled.
Signed-off-by: Gary R Hook <gary.hook@xxxxxxx>
---
drivers/iommu/Kconfig | 4 ++++
drivers/iommu/Makefile | 1 +
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 | 5 +++++
6 files changed, 59 insertions(+), 2 deletions(-)
create mode 100644 drivers/iommu/amd_iommu_debugfs.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f9af25ac409f..ec223f6f4ad4 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -137,6 +137,10 @@ config AMD_IOMMU
your BIOS for an option to enable it or if you have an IVRS ACPI
table.
+config AMD_IOMMU_DEBUGFS
+ def_bool y
Why default y? Can you not boot a box without this? If not, it should
not be Y.
Again, apologies for not seeing this sooner.
Yes, the system can boot without this. The idea of a hidden option was
surfaced by Robin, and after my first approach was shot down, I tried this.
Logic: If the over-arching IOMMU debugfs option is enabled, then
AMD_IOMMU_DEBUGFS gets defined, and AMD IOMMU code gets included.
This issue was discussed a few weeks ago. No single approach appears to
satisfy everyone. I like this because it depends upon one switch: Do you
want DebugFS support enabled in the IOMMU driver, period?
Vendor-specific code can then choose to implement support or not, and a
builder doesn't have to worry about enabling/disabling multiple Kconfig
options.
At least, that was my line of reasoning.
I'm not married to any approach, and I don't find clever use of Kconfig
options too terribly challenging. And I'm not defending, I'm just
explaining.
+ depends on AMD_IOMMU && IOMMU_DEBUGFS
+
config AMD_IOMMU_V2
tristate "AMD IOMMU Version 2 driver"
depends on AMD_IOMMU
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 74cfbc392862..47fd6ea9de2d 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_IOMMU_IOVA) += iova.o
obj-$(CONFIG_OF_IOMMU) += of_iommu.o
obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o
obj-$(CONFIG_AMD_IOMMU) += amd_iommu.o amd_iommu_init.o
+obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += amd_iommu_debugfs.o
obj-$(CONFIG_AMD_IOMMU_V2) += amd_iommu_v2.o
obj-$(CONFIG_ARM_SMMU) += arm-smmu.o
obj-$(CONFIG_ARM_SMMU_V3) += arm-smmu-v3.o
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@xxxxxxx>
+ */
+
+#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) {
Do not test this.
Okay, noted. I'll stop worrying about this.
+ snprintf(name, MAX_NAME_LEN, "iommu%02d", iommu->index);
+ iommu->debugfs = debugfs_create_dir(name,
+ amd_iommu_debugfs);
+ if (!iommu->debugfs) {
No, you don't care about the return value of any debugfs call. Just
save the directory and move on. If it's not correct, find, nothing is
wrong, just keep going.
Roger.
Thank you,
Gary