iommu/vt-d: Add the document for Intel IOMMU debugfs

This document guides users to dump the Intel IOMMU internals by debugfs.
Signed-off-by: Jingqi Liu <Jingqi.liu@intel.com>
Link: https://lore.kernel.org/r/20240207090742.23857-1-Jingqi.liu@intel.comSigned-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Documentation/ABI/testing/debugfs-intel-iommu

+What:		/sys/kernel/debug/iommu/intel/iommu_regset
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file dumps all the register contents for each IOMMU device.
+
+		Example in Kabylake:
+
+		::
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/iommu_regset
+
+		 IOMMU: dmar0 Register Base Address: 26be37000
+
+		 Name                    Offset          Contents
+		 VER                     0x00            0x0000000000000010
+		 GCMD                    0x18            0x0000000000000000
+		 GSTS                    0x1c            0x00000000c7000000
+		 FSTS                    0x34            0x0000000000000000
+		 FECTL                   0x38            0x0000000000000000
+
+		 [...]
+
+		 IOMMU: dmar1 Register Base Address: fed90000
+
+		 Name                    Offset          Contents
+		 VER                     0x00            0x0000000000000010
+		 GCMD                    0x18            0x0000000000000000
+		 GSTS                    0x1c            0x00000000c7000000
+		 FSTS                    0x34            0x0000000000000000
+		 FECTL                   0x38            0x0000000000000000
+
+		 [...]
+
+		 IOMMU: dmar2 Register Base Address: fed91000
+
+		 Name                    Offset          Contents
+		 VER                     0x00            0x0000000000000010
+		 GCMD                    0x18            0x0000000000000000
+		 GSTS                    0x1c            0x00000000c7000000
+		 FSTS                    0x34            0x0000000000000000
+		 FECTL                   0x38            0x0000000000000000
+
+		 [...]
+
+What:		/sys/kernel/debug/iommu/intel/ir_translation_struct
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file dumps the table entries for Interrupt
+		remapping and Interrupt posting.
+
+		Example in Kabylake:
+
+		::
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/ir_translation_struct
+
+		 Remapped Interrupt supported on IOMMU: dmar0
+		 IR table address:100900000
+
+		 Entry SrcID   DstID    Vct IRTE_high           IRTE_low
+		 0     00:0a.0 00000080 24  0000000000040050    000000800024000d
+		 1     00:0a.0 00000001 ef  0000000000040050    0000000100ef000d
+
+		 Remapped Interrupt supported on IOMMU: dmar1
+		 IR table address:100300000
+		 Entry SrcID   DstID    Vct IRTE_high           IRTE_low
+		 0     00:02.0 00000002 26  0000000000040010    000000020026000d
+
+		 [...]
+
+		 ****
+
+		 Posted Interrupt supported on IOMMU: dmar0
+		 IR table address:100900000
+		 Entry SrcID   PDA_high PDA_low  Vct IRTE_high          IRTE_low
+
+What:		/sys/kernel/debug/iommu/intel/dmar_translation_struct
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file dumps Intel IOMMU DMA remapping tables, such
+		as root table, context table, PASID directory and PASID
+		table entries in debugfs. For legacy mode, it doesn't
+		support PASID, and hence PASID field is defaulted to
+		'-1' and other PASID related fields are invalid.
+
+		Example in Kabylake:
+
+		::
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/dmar_translation_struct
+
+		 IOMMU dmar1: Root Table Address: 0x103027000
+		 B.D.F   Root_entry
+		 00:02.0 0x0000000000000000:0x000000010303e001
+
+		 Context_entry
+		 0x0000000000000102:0x000000010303f005
+
+		 PASID   PASID_table_entry
+		 -1      0x0000000000000000:0x0000000000000000:0x0000000000000000
+
+		 IOMMU dmar0: Root Table Address: 0x103028000
+		 B.D.F   Root_entry
+		 00:0a.0 0x0000000000000000:0x00000001038a7001
+
+		 Context_entry
+		 0x0000000000000000:0x0000000103220e7d
+
+		 PASID   PASID_table_entry
+		 0       0x0000000000000000:0x0000000000800002:0x00000001038a5089
+
+		 [...]
+
+What:		/sys/kernel/debug/iommu/intel/invalidation_queue
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file exports invalidation queue internals of each
+		IOMMU device.
+
+		Example in Kabylake:
+
+		::
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/invalidation_queue
+
+		 Invalidation queue on IOMMU: dmar0
+		 Base: 0x10022e000      Head: 20        Tail: 20
+		 Index          qw0                    qw1                     qw2
+		     0   0000000000000014        0000000000000000        0000000000000000
+		     1   0000000200000025        0000000100059c04        0000000000000000
+		     2   0000000000000014        0000000000000000        0000000000000000
+
+				qw3                  status
+			 0000000000000000        0000000000000000
+			 0000000000000000        0000000000000000
+			 0000000000000000        0000000000000000
+
+		 [...]
+
+		 Invalidation queue on IOMMU: dmar1
+		 Base: 0x10026e000      Head: 32        Tail: 32
+		 Index           qw0                     qw1                   status
+		     0   0000000000000004        0000000000000000         0000000000000000
+		     1   0000000200000025        0000000100059804         0000000000000000
+		     2   0000000000000011        0000000000000000         0000000000000000
+
+		 [...]
+
+What:		/sys/kernel/debug/iommu/intel/dmar_perf_latency
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file is used to control and show counts of
+		execution time ranges for various types per DMAR.
+
+		Firstly, write a value to
+		/sys/kernel/debug/iommu/intel/dmar_perf_latency
+		to enable sampling.
+
+		The possible values are as follows:
+
+		* 0 - disable sampling all latency data
+
+		* 1 - enable sampling IOTLB invalidation latency data
+
+		* 2 - enable sampling devTLB invalidation latency data
+
+		* 3 - enable sampling intr entry cache invalidation latency data
+
+		Next, read /sys/kernel/debug/iommu/intel/dmar_perf_latency gives
+		a snapshot of sampling result of all enabled monitors.
+
+		Examples in Kabylake:
+
+		::
+
+		 1) Disable sampling all latency data:
+
+		 $ sudo echo 0 > /sys/kernel/debug/iommu/intel/dmar_perf_latency
+
+		 2) Enable sampling IOTLB invalidation latency data
+
+		 $ sudo echo 1 > /sys/kernel/debug/iommu/intel/dmar_perf_latency
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/dmar_perf_latency
+
+		 IOMMU: dmar0 Register Base Address: 26be37000
+				 <0.1us   0.1us-1us    1us-10us  10us-100us   100us-1ms
+		 inv_iotlb           0           0           0           0           0
+
+				 1ms-10ms      >=10ms     min(us)     max(us) average(us)
+		 inv_iotlb           0           0           0           0           0
+
+		 [...]
+
+		 IOMMU: dmar2 Register Base Address: fed91000
+				 <0.1us   0.1us-1us    1us-10us  10us-100us   100us-1ms
+		 inv_iotlb           0           0          18           0           0
+
+				 1ms-10ms      >=10ms     min(us)     max(us) average(us)
+		 inv_iotlb           0           0           2           2           2
+
+		 3) Enable sampling devTLB invalidation latency data
+
+		 $ sudo echo 2 > /sys/kernel/debug/iommu/intel/dmar_perf_latency
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/dmar_perf_latency
+
+		 IOMMU: dmar0 Register Base Address: 26be37000
+				 <0.1us   0.1us-1us    1us-10us  10us-100us   100us-1ms
+		 inv_devtlb           0           0           0           0           0
+
+				 >=10ms     min(us)     max(us) average(us)
+		 inv_devtlb           0           0           0           0
+
+		 [...]
+
+What:		/sys/kernel/debug/iommu/intel/<bdf>/domain_translation_struct
+Date:		December 2023
+Contact:	Jingqi Liu <Jingqi.liu@intel.com>
+Description:
+		This file dumps a specified page table of Intel IOMMU
+		in legacy mode or scalable mode.
+
+		For a device that only supports legacy mode, dump its
+		page table by the debugfs file in the debugfs device
+		directory. e.g.
+		/sys/kernel/debug/iommu/intel/0000:00:02.0/domain_translation_struct.
+
+		For a device that supports scalable mode, dump the
+		page table of specified pasid by the debugfs file in
+		the debugfs pasid directory. e.g.
+		/sys/kernel/debug/iommu/intel/0000:00:02.0/1/domain_translation_struct.
+
+		Examples in Kabylake:
+
+		::
+
+		 1) Dump the page table of device "0000:00:02.0" that only supports legacy mode.
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/0000:00:02.0/domain_translation_struct
+
+		 Device 0000:00:02.0 @0x1017f8000
+		 IOVA_PFN                PML5E                   PML4E
+		 0x000000008d800 |       0x0000000000000000      0x00000001017f9003
+		 0x000000008d801 |       0x0000000000000000      0x00000001017f9003
+		 0x000000008d802 |       0x0000000000000000      0x00000001017f9003
+
+		 PDPE                    PDE                     PTE
+		 0x00000001017fa003      0x00000001017fb003      0x000000008d800003
+		 0x00000001017fa003      0x00000001017fb003      0x000000008d801003
+		 0x00000001017fa003      0x00000001017fb003      0x000000008d802003
+
+		 [...]
+
+		 2) Dump the page table of device "0000:00:0a.0" with PASID "1" that
+		 supports scalable mode.
+
+		 $ sudo cat /sys/kernel/debug/iommu/intel/0000:00:0a.0/1/domain_translation_struct
+
+		 Device 0000:00:0a.0 with pasid 1 @0x10c112000
+		 IOVA_PFN                PML5E                   PML4E
+		 0x0000000000000 |       0x0000000000000000      0x000000010df93003
+		 0x0000000000001 |       0x0000000000000000      0x000000010df93003
+		 0x0000000000002 |       0x0000000000000000      0x000000010df93003
+
+		 PDPE                    PDE                     PTE
+		 0x0000000106ae6003      0x0000000104b38003      0x0000000147c00803
+		 0x0000000106ae6003      0x0000000104b38003      0x0000000147c01803
+		 0x0000000106ae6003      0x0000000104b38003      0x0000000147c02803
+
+		 [...]