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/** @file
Type and macro definitions specific to the Virtio Filesystem device.
At the time of this writing, the latest released Virtio specification (v1.1)
does not include the virtio-fs device. The development version of the
specification defines it however; see the latest version at
<https://github.com/oasis-tcs/virtio-spec/blob/87fa6b5d8155/virtio-fs.tex>.
This header file is minimal, and only defines the types and macros that are
necessary for the OvmfPkg implementation.
Copyright (C) 2020, Red Hat, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#ifndef VIRTIO_FS_H_
#define VIRTIO_FS_H_
#include <IndustryStandard/Virtio.h>
//
// Lowest numbered queue for sending normal priority requests.
//
#define VIRTIO_FS_REQUEST_QUEUE 1
//
// Number of bytes in the "VIRTIO_FS_CONFIG.Tag" field.
//
#define VIRTIO_FS_TAG_BYTES 36
//
// Device configuration layout.
//
#pragma pack (1)
typedef struct {
//
// The Tag field can be considered the filesystem label, or a mount point
// hint. It is UTF-8 encoded, and padded to full size with NUL bytes. If the
// encoded bytes take up the entire Tag field, then there is no NUL
// terminator.
//
UINT8 Tag[VIRTIO_FS_TAG_BYTES];
//
// The total number of request virtqueues exposed by the device (i.e.,
// excluding the "hiprio" queue).
//
UINT32 NumReqQueues;
} VIRTIO_FS_CONFIG;
#pragma pack ()
//
// FUSE-related definitions follow.
//
// From virtio-v1.1-cs01-87fa6b5d8155, 5.11 File System Device: "[...] The
// driver acts as the FUSE client mounting the file system. The virtio file
// system device provides the mechanism for transporting FUSE requests [...]"
//
// Unfortunately, the documentation of the FUSE wire protocol is lacking. The
// Virtio spec (as of this writing) simply defers to
// "include/uapi/linux/fuse.h" in the Linux kernel source -- see the reference
// in virtio spec file "introduction.tex", at commit 87fa6b5d8155.
//
// Of course, "include/uapi/linux/fuse.h" is a moving target (the virtio spec
// does not specify a particular FUSE interface version). The OvmfPkg code
// targets version 7.31, because that's the lowest version that the QEMU
// virtio-fs daemon supports at this time -- see QEMU commit 72c42e2d6551
// ("virtiofsd: Trim out compatibility code", 2020-01-23).
//
// Correspondingly, Linux's "include/uapi/linux/fuse.h" is consulted as checked
// out at commit (c6ff213fe5b8^) = d78092e4937d ("fuse: fix page dereference
// after free", 2020-09-18); that is, right before commit c6ff213fe5b8 ("fuse:
// add submount support to <uapi/linux/fuse.h>", 2020-09-18) introduces FUSE
// interface version 7.32.
//
#define VIRTIO_FS_FUSE_MAJOR 7
#define VIRTIO_FS_FUSE_MINOR 31
#pragma pack (1)
//
// Request-response headers common to all request types.
//
typedef struct {
UINT32 Len;
UINT32 Opcode;
UINT64 Unique;
UINT64 NodeId;
UINT32 Uid;
UINT32 Gid;
UINT32 Pid;
UINT32 Padding;
} VIRTIO_FS_FUSE_REQUEST;
typedef struct {
UINT32 Len;
INT32 Error;
UINT64 Unique;
} VIRTIO_FS_FUSE_RESPONSE;
#pragma pack ()
#endif // VIRTIO_FS_H_
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