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Message-ID: <f372c5da-97c0-8029-b402-72072472d9a5@amd.com> Date: Fri, 30 Mar 2018 13:41:44 -0500 From: Gary R Hook <gary.hook@....com> To: Tom Lendacky <thomas.lendacky@....com>, iommu@...ts.linux-foundation.org Cc: joro@...tes.org, jacob.jun.pan@...ux.intel.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/2] iommu - Enable debugfs exposure of the IOMMU 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@....com> >> --- >> 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@....com> >> + */ >> + >> +#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 */ >>
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