OvmfPkg/Include/IndustryStandard/VirtioFs.h

   1 /** @file
   2   Type and macro definitions specific to the Virtio Filesystem device.
   3
   4   At the time of this writing, the latest released Virtio specification (v1.1)
   5   does not include the virtio-fs device. The development version of the
   6   specification defines it however; see the latest version at
   7   <https://github.com/oasis-tcs/virtio-spec/blob/87fa6b5d8155/virtio-fs.tex>.
   8
   9   This header file is minimal, and only defines the types and macros that are
  10   necessary for the OvmfPkg implementation.
  11
  12   Copyright (C) 2020, Red Hat, Inc.
  13
  14   SPDX-License-Identifier: BSD-2-Clause-Patent
  15 **/
  16
  17 #ifndef VIRTIO_FS_H_
  18 #define VIRTIO_FS_H_
  19
  20 #include <IndustryStandard/Virtio.h>
  21
  22 //
  23 // Lowest numbered queue for sending normal priority requests.
  24 //
  25 #define VIRTIO_FS_REQUEST_QUEUE 1
  26
  27 //
  28 // Number of bytes in the "VIRTIO_FS_CONFIG.Tag" field.
  29 //
  30 #define VIRTIO_FS_TAG_BYTES 36
  31
  32 //
  33 // Device configuration layout.
  34 //
  35 #pragma pack (1)
  36 typedef struct {
  37   //
  38   // The Tag field can be considered the filesystem label, or a mount point
  39   // hint. It is UTF-8 encoded, and padded to full size with NUL bytes. If the
  40   // encoded bytes take up the entire Tag field, then there is no NUL
  41   // terminator.
  42   //
  43   UINT8 Tag[VIRTIO_FS_TAG_BYTES];
  44   //
  45   // The total number of request virtqueues exposed by the device (i.e.,
  46   // excluding the "hiprio" queue).
  47   //
  48   UINT32 NumReqQueues;
  49 } VIRTIO_FS_CONFIG;
  50 #pragma pack ()
  51
  52 //
  53 // FUSE-related definitions follow.
  54 //
  55 // From virtio-v1.1-cs01-87fa6b5d8155, 5.11 File System Device: "[...] The
  56 // driver acts as the FUSE client mounting the file system. The virtio file
  57 // system device provides the mechanism for transporting FUSE requests [...]"
  58 //
  59 // Unfortunately, the documentation of the FUSE wire protocol is lacking. The
  60 // Virtio spec (as of this writing) simply defers to
  61 // "include/uapi/linux/fuse.h" in the Linux kernel source -- see the reference
  62 // in virtio spec file "introduction.tex", at commit 87fa6b5d8155.
  63 //
  64 // Of course, "include/uapi/linux/fuse.h" is a moving target (the virtio spec
  65 // does not specify a particular FUSE interface version). The OvmfPkg code
  66 // targets version 7.31, because that's the lowest version that the QEMU
  67 // virtio-fs daemon supports at this time -- see QEMU commit 72c42e2d6551
  68 // ("virtiofsd: Trim out compatibility code", 2020-01-23).
  69 //
  70 // Correspondingly, Linux's "include/uapi/linux/fuse.h" is consulted as checked
  71 // out at commit (c6ff213fe5b8^) = d78092e4937d ("fuse: fix page dereference
  72 // after free", 2020-09-18); that is, right before commit c6ff213fe5b8 ("fuse:
  73 // add submount support to <uapi/linux/fuse.h>", 2020-09-18) introduces FUSE
  74 // interface version 7.32.
  75 //
  76 #define VIRTIO_FS_FUSE_MAJOR  7
  77 #define VIRTIO_FS_FUSE_MINOR 31
  78
  79 //
  80 // FUSE operation codes.
  81 //
  82 typedef enum {
  83   VirtioFsFuseOpInit        = 26,
  84   VirtioFsFuseOpOpenDir     = 27,
  85 } VIRTIO_FS_FUSE_OPCODE;
  86
  87 #pragma pack (1)
  88 //
  89 // Request-response headers common to all request types.
  90 //
  91 typedef struct {
  92   UINT32 Len;
  93   UINT32 Opcode;
  94   UINT64 Unique;
  95   UINT64 NodeId;
  96   UINT32 Uid;
  97   UINT32 Gid;
  98   UINT32 Pid;
  99   UINT32 Padding;
 100 } VIRTIO_FS_FUSE_REQUEST;
 101
 102 typedef struct {
 103   UINT32 Len;
 104   INT32  Error;
 105   UINT64 Unique;
 106 } VIRTIO_FS_FUSE_RESPONSE;
 107
 108 //
 109 // Headers for VirtioFsFuseOpInit.
 110 //
 111 typedef struct {
 112   UINT32 Major;
 113   UINT32 Minor;
 114   UINT32 MaxReadahead;
 115   UINT32 Flags;
 116 } VIRTIO_FS_FUSE_INIT_REQUEST;
 117
 118 typedef struct {
 119   UINT32 Major;
 120   UINT32 Minor;
 121   UINT32 MaxReadahead;
 122   UINT32 Flags;
 123   UINT16 MaxBackground;
 124   UINT16 CongestionThreshold;
 125   UINT32 MaxWrite;
 126   UINT32 TimeGran;
 127   UINT16 MaxPages;
 128   UINT16 MapAlignment;
 129   UINT32 Unused[8];
 130 } VIRTIO_FS_FUSE_INIT_RESPONSE;
 131
 132 //
 133 // Headers for VirtioFsFuseOpOpenDir.
 134 //
 135 typedef struct {
 136   UINT32 Flags;
 137   UINT32 Unused;
 138 } VIRTIO_FS_FUSE_OPEN_REQUEST;
 139
 140 typedef struct {
 141   UINT64 FileHandle;
 142   UINT32 OpenFlags;
 143   UINT32 Padding;
 144 } VIRTIO_FS_FUSE_OPEN_RESPONSE;
 145 #pragma pack ()
 146
 147 #endif // VIRTIO_FS_H_