Re: [PATCH 1/2] iommu - Enable debugfs exposure of the IOMMU
From: Gary R Hook
Date: Fri Mar 30 2018 - 14:43:19 EST
On 03/29/2018 10:57 PM, Tom Lendacky wrote:
On 3/29/2018 5:54 PM, Gary R Hook wrote:
Provide base enablement for using debugfs to expose internal data of
an IOMMU driver. When enabled, create the /sys/kernel/debug/iommu
So this can't actually create anything yet since nothing invokes the
function. Maybe describe how it should be used by other drivers (and
probably include that description as a commment for the function) to
create the directory.
Exactly. Given the approach I took, it takes another patch to take
advantage of this. I can certainly elaborate on usage if we agree that
this framework is acceptable.
directory. Emit a strong warning at boot time to indicate that this
feature is enabled.
Signed-off-by: Gary R Hook <gary.hook@xxxxxxx>
---
drivers/iommu/Kconfig | 11 +++++++++++
drivers/iommu/Makefile | 2 ++
drivers/iommu/amd_iommu_init.c | 2 ++
drivers/iommu/iommu-debugfs.c | 32 ++++++++++++++++++++++++++++++++
include/linux/iommu.h | 4 ++++
5 files changed, 51 insertions(+)
create mode 100644 drivers/iommu/iommu-debugfs.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f3a21343e636..c1e39dabfec2 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
endmenu
+config IOMMU_DEBUG
+ 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..5e5c3339681d 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_DEBUG) += iommu-debugfs.o
obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
@@ -10,6 +11,7 @@ obj-$(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_DEBUG) += amd_iommu_debugfs.o
Where is this CONFIG defined?
That, my friend is left-over cruft. Please ignore. Apologies, and thanks.
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_init.c b/drivers/iommu/amd_iommu_init.c
index 6fe2d0346073..99d48c42a12f 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -2783,6 +2783,8 @@ int __init amd_iommu_detect(void)
iommu_detected = 1;
x86_init.iommu.iommu_init = amd_iommu_init;
+dump_stack();
+
This definitely shouldn't be here.
Dang it!
return 1;
}
diff --git a/drivers/iommu/iommu-debugfs.c b/drivers/iommu/iommu-debugfs.c
new file mode 100644
index 000000000000..94c9acc63b65
--- /dev/null
+++ b/drivers/iommu/iommu-debugfs.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD IOMMU driver
This isn't the AMD IOMMU driver.
Again: dang it!
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook@xxxxxxx>
+ */
+
+#include <linux/pci.h>
+#include <linux/iommu.h>
+#include <linux/debugfs.h>
+
+static struct dentry *iommu_debugfs_dir;
+
+#define MAX_NAME_LEN 20
This isn't used anywhere.
Thanks.
+
+/* Return a zero on failure; 1 on successful setup */
Return NULL on failure, pointer to IOMMU debugfs dentry on success.
Roger.
+struct dentry *iommu_debugfs_setup(void)
+{
+ if (!debugfs_initialized())
+ return NULL;
+
+ 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 41b8c5757859..cb2957dac43b 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -696,6 +696,10 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
return NULL;
}
+#ifdef CONFIG_IOMMU_DEBUG
Should be a space between the #ifdef and the CONFIG_..., not a tab.
Roger that.
Thanks,
Tom
+struct dentry *iommu_debugfs_setup(void);
+#endif
+
#endif /* CONFIG_IOMMU_API */
#endif /* __LINUX_IOMMU_H */