ACPI DMARメモ

linux acpi
  • IOMMUの情報はACPIのDMARに格納されている
  • DMARのデータ構造は，Intel VT-d ドキュメント (Intel® Virtualization Technology for Directed I/O) の8章に書いてある
  • ざっくり以下のような構造
    • DMAR (DMA Remapping Table)
      • DRHD (DMA Remapping Hardware Unite Definition) (n個)
      • RMRR (Reserved Memory Region Reporting) (m個)
      • ATSR (ATS Capability Reporintg) (l個)
  • DRHDがIOMMUの情報
    • IOMMUが対象とするPCIデバイスの番号が格納される
      • SegmentがPCI segment番号, PCI Bus NumberとPCI Pathが bus, device, function 番号
    • Flags = 0x1 (INCLUDE_PCI_ALL) のとき，PCI segmentに含まれる全てのPCI EndpointがこのIOMMUの対象
      • ただし，別のIOMMUで既に対象となっているデバイスは除く
  • RMRRはDMAに使えない予約済みメモリ領域の情報

DMAR tableの例 (Core i7-7770, ASRock Z270 Extreme4)

% sudo cp /sys/firmware/acpi/tables/DMAR
% iasl -d DMAR
% cat DMAR.dsl
/*
 * Intel ACPI Component Architecture
 * AML/ASL+ Disassembler version 20160108-64
 * Copyright (c) 2000 - 2016 Intel Corporation
 * 
 * Disassembly of DMAR, Sat Mar 10 21:19:40 2018
 *
 * ACPI Data Table [DMAR]
 *
 * Format: [HexOffset DecimalOffset ByteLength]  FieldName : FieldValue
 */

[000h 0000   4]                    Signature : "DMAR"    [DMA Remapping table]
[004h 0004   4]                 Table Length : 000000A8
[008h 0008   1]                     Revision : 01
[009h 0009   1]                     Checksum : D2
[00Ah 0010   6]                       Oem ID : "INTEL "
[010h 0016   8]                 Oem Table ID : "KBL "
[018h 0024   4]                 Oem Revision : 00000001
[01Ch 0028   4]              Asl Compiler ID : "INTL"
[020h 0032   4]        Asl Compiler Revision : 00000001

[024h 0036   1]           Host Address Width : 26
[025h 0037   1]                        Flags : 01
[026h 0038  10]                     Reserved : 00 00 00 00 00 00 00 00 00 00

[030h 0048   2]                Subtable Type : 0000 [Hardware Unit Definition]
[032h 0050   2]                       Length : 0018

[034h 0052   1]                        Flags : 00
[035h 0053   1]                     Reserved : 00
[036h 0054   2]           PCI Segment Number : 0000
[038h 0056   8]        Register Base Address : 00000000FED90000

[040h 0064   1]            Device Scope Type : 01 [PCI Endpoint Device]
[041h 0065   1]                 Entry Length : 08
[042h 0066   2]                     Reserved : 0000
[044h 0068   1]               Enumeration ID : 00
[045h 0069   1]               PCI Bus Number : 00

[046h 0070   2]                     PCI Path : 02,00


[048h 0072   2]                Subtable Type : 0000 [Hardware Unit Definition]
[04Ah 0074   2]                       Length : 0020

[04Ch 0076   1]                        Flags : 01
[04Dh 0077   1]                     Reserved : 00
[04Eh 0078   2]           PCI Segment Number : 0000
[050h 0080   8]        Register Base Address : 00000000FED91000

[058h 0088   1]            Device Scope Type : 03 [IOAPIC Device]
[059h 0089   1]                 Entry Length : 08
[05Ah 0090   2]                     Reserved : 0000
[05Ch 0092   1]               Enumeration ID : 02
[05Dh 0093   1]               PCI Bus Number : F0

[05Eh 0094   2]                     PCI Path : 1F,00


[060h 0096   1]            Device Scope Type : 04 [Message-capable HPET Device]
[061h 0097   1]                 Entry Length : 08
[062h 0098   2]                     Reserved : 0000
[064h 0100   1]               Enumeration ID : 00
[065h 0101   1]               PCI Bus Number : 00

[066h 0102   2]                     PCI Path : 1F,00


[068h 0104   2]                Subtable Type : 0001 [Reserved Memory Region]
[06Ah 0106   2]                       Length : 0020

[06Ch 0108   2]                     Reserved : 0000
[06Eh 0110   2]           PCI Segment Number : 0000
[070h 0112   8]                 Base Address : 000000007E091000
[078h 0120   8]          End Address (limit) : 000000007E0B0FFF

[080h 0128   1]            Device Scope Type : 01 [PCI Endpoint Device]
[081h 0129   1]                 Entry Length : 08
[082h 0130   2]                     Reserved : 0000
[084h 0132   1]               Enumeration ID : 00
[085h 0133   1]               PCI Bus Number : 00

[086h 0134   2]                     PCI Path : 14,00


[088h 0136   2]                Subtable Type : 0001 [Reserved Memory Region]
[08Ah 0138   2]                       Length : 0020

[08Ch 0140   2]                     Reserved : 0000
[08Eh 0142   2]           PCI Segment Number : 0000
[090h 0144   8]                 Base Address : 000000007F800000
[098h 0152   8]          End Address (limit) : 000000008FFFFFFF

[0A0h 0160   1]            Device Scope Type : 01 [PCI Endpoint Device]
[0A1h 0161   1]                 Entry Length : 08
[0A2h 0162   2]                     Reserved : 0000
[0A4h 0164   1]               Enumeration ID : 00
[0A5h 0165   1]               PCI Bus Number : 00

[0A6h 0166   2]                     PCI Path : 02,00


Raw Table Data: Length 168 (0xA8)

  0000: 44 4D 41 52 A8 00 00 00 01 D2 49 4E 54 45 4C 20  // DMAR......INTEL 
  0010: 4B 42 4C 20 00 00 00 00 01 00 00 00 49 4E 54 4C  // KBL ........INTL
  0020: 01 00 00 00 26 01 00 00 00 00 00 00 00 00 00 00  // ....&...........
  0030: 00 00 18 00 00 00 00 00 00 00 D9 FE 00 00 00 00  // ................
  0040: 01 08 00 00 00 00 02 00 00 00 20 00 01 00 00 00  // .......... .....
  0050: 00 10 D9 FE 00 00 00 00 03 08 00 00 02 F0 1F 00  // ................
  0060: 04 08 00 00 00 00 1F 00 01 00 20 00 00 00 00 00  // .......... .....
  0070: 00 10 09 7E 00 00 00 00 FF 0F 0B 7E 00 00 00 00  // ...~.......~....
  0080: 01 08 00 00 00 00 14 00 01 00 20 00 00 00 00 00  // .......... .....
  0090: 00 00 80 7F 00 00 00 00 FF FF FF 8F 00 00 00 00  // ................
  00A0: 01 08 00 00 00 00 02 00                          // ........
  • [Hardware Unit Definition] がDRHD
  • このマシンだと2つIOMMUがあって，一つが 0000:02:00のデバイスを管理，もう一つがセグメント0000の全てのPCIデバイスを管理
    • ちなみに，0000:00:02.0は VGA compatible controller: Intel Corporation Device 5912 (rev 04)
    • なぜこれが別のIOMMUなのかは分からない