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 // The inode number of the root directory.
  81 //
  82 #define VIRTIO_FS_FUSE_ROOT_DIR_NODE_ID 1
  83
  84 //
  85 // FUSE operation codes.
  86 //
  87 typedef enum {
  88   VirtioFsFuseOpRelease     = 18,
  89   VirtioFsFuseOpInit        = 26,
  90   VirtioFsFuseOpOpenDir     = 27,
  91   VirtioFsFuseOpReleaseDir  = 29,
  92 } VIRTIO_FS_FUSE_OPCODE;
  93
  94 #pragma pack (1)
  95 //
  96 // Request-response headers common to all request types.
  97 //
  98 typedef struct {
  99   UINT32 Len;
 100   UINT32 Opcode;
 101   UINT64 Unique;
 102   UINT64 NodeId;
 103   UINT32 Uid;
 104   UINT32 Gid;
 105   UINT32 Pid;
 106   UINT32 Padding;
 107 } VIRTIO_FS_FUSE_REQUEST;
 108
 109 typedef struct {
 110   UINT32 Len;
 111   INT32  Error;
 112   UINT64 Unique;
 113 } VIRTIO_FS_FUSE_RESPONSE;
 114
 115 //
 116 // Header for VirtioFsFuseOpRelease and VirtioFsFuseOpReleaseDir.
 117 //
 118 typedef struct {
 119   UINT64 FileHandle;
 120   UINT32 Flags;
 121   UINT32 ReleaseFlags;
 122   UINT64 LockOwner;
 123 } VIRTIO_FS_FUSE_RELEASE_REQUEST;
 124
 125 //
 126 // Headers for VirtioFsFuseOpInit.
 127 //
 128 typedef struct {
 129   UINT32 Major;
 130   UINT32 Minor;
 131   UINT32 MaxReadahead;
 132   UINT32 Flags;
 133 } VIRTIO_FS_FUSE_INIT_REQUEST;
 134
 135 typedef struct {
 136   UINT32 Major;
 137   UINT32 Minor;
 138   UINT32 MaxReadahead;
 139   UINT32 Flags;
 140   UINT16 MaxBackground;
 141   UINT16 CongestionThreshold;
 142   UINT32 MaxWrite;
 143   UINT32 TimeGran;
 144   UINT16 MaxPages;
 145   UINT16 MapAlignment;
 146   UINT32 Unused[8];
 147 } VIRTIO_FS_FUSE_INIT_RESPONSE;
 148
 149 //
 150 // Headers for VirtioFsFuseOpOpenDir.
 151 //
 152 typedef struct {
 153   UINT32 Flags;
 154   UINT32 Unused;
 155 } VIRTIO_FS_FUSE_OPEN_REQUEST;
 156
 157 typedef struct {
 158   UINT64 FileHandle;
 159   UINT32 OpenFlags;
 160   UINT32 Padding;
 161 } VIRTIO_FS_FUSE_OPEN_RESPONSE;
 162 #pragma pack ()
 163
 164 #endif // VIRTIO_FS_H_