virtio: add virtiofs

doc/LICENSING.rst

@@ -108,6 +108,15 @@ Python Devicetree library test files
 
   * Various yaml files under ``scripts/dts/python-devicetree/tests``
 
+FUSE Interface Definition Header File
+--------------------------------------
+
+* *Licensing:* `BSD-2-clause`_
+* *Impact:* This header is used in Zephyr build only if :kconfig:option:`CONFIG_FUSE_CLIENT` is enabled.
+* *Files*:
+
+  * :zephyr_file:`subsys/fs/fuse_client/fuse_abi.h`
+
 .. _Apache 2.0 License:
    https://github.com/zephyrproject-rtos/zephyr/blob/main/LICENSE
 
@@ -120,6 +129,9 @@ Python Devicetree library test files
 .. _BSD-3-clause:
    https://opensource.org/license/bsd-3-clause
 
+.. _BSD-2-clause:
+   https://opensource.org/license/bsd-2-clause
+
 .. _Coccinelle:
    https://coccinelle.gitlabpages.inria.fr/website/
 

doc/hardware/virtualization/virtio.rst

@@ -123,6 +123,31 @@ virtqueue has to be acquired using :c:func:`virtio_get_virtqueue`. To send data
 will be invoked once the device returns the given descriptor chain. After that, the virtqueue has to be notified using
 :c:func:`virtio_notify_virtqueue` from the Virtio API.
 
+Guest-side Virtio drivers
+*************************
+Currently Zephyr provides drivers for Virtio over PCI and Virtio over MMIO and drivers for two devices using virtio - virtiofs, used
+to access the filesystem of the host and virtio-entropy, used as an entropy source.
+
+Virtiofs
+=========
+This driver provides support for `virtiofs <https://virtio-fs.gitlab.io/>`_ - a filesystem allowing a virtual machine guest to access
+a directory on the host. It uses FUSE messages to communicate between the host and the guest in order to perform filesystem operations such as
+opening and reading files. Every time the guest wants to perform some filesystem operation it places in the virtqueue a descriptor chain
+starting with the device readable part, containing the FUSE input header and input data, and ending it with the device writeable part, with place
+for the FUSE output header and output data.
+
+Virtio-entropy
+==============
+This driver allows using virtio-entropy as an entropy source in Zephyr. The operation of this device is simple - the driver places a
+buffer in the virtqueue and receives it back, filled with random data.
+
+Virtio samples
+**************
+A sample showcasing the use of a driver relying on Virtio is provided in :zephyr:code-sample:`virtiofs`. If you wish
+to check code interfacing directly with the Virtio driver, you can check the virtiofs driver, especially :c:func:`virtiofs_init`
+for initialization and :c:func:`virtiofs_send_receive` with the :c:func:`virtiofs_recv_cb` for data transfer to/from
+the Virtio device.
+
 API Reference
 *************
 

include/zephyr/fs/fs.h

@@ -61,6 +61,9 @@ enum {
 	/** Identifier for in-tree Ext2 file system. */
 	FS_EXT2,
 
+	/** Identifier for in-tree Virtiofs file system. */
+	FS_VIRTIOFS,
+
 	/** Base identifier for external file systems. */
 	FS_TYPE_EXTERNAL_BASE,
 };

include/zephyr/fs/fs_interface.h

@@ -50,6 +50,10 @@ extern "C" {
 #define MAX_FILE_NAME 255
 #endif
 
+#if !defined(MAX_FILE_NAME) && defined(CONFIG_FILE_SYSTEM_VIRTIOFS)
+#define MAX_FILE_NAME 255
+#endif
+
 #if !defined(MAX_FILE_NAME) /* filesystem selection */
 /* Use standard 8.3 when no filesystem is explicitly selected */
 #define MAX_FILE_NAME 12

include/zephyr/fs/virtiofs.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2025 Antmicro <www.antmicro.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_FS_VIRTIOFS_H_
+#define ZEPHYR_INCLUDE_FS_VIRTIOFS_H_
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct virtiofs_fs_data {
+	uint32_t max_write;
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_FS_VIRTIOFS_H_ */

samples/subsys/fs/virtiofs/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(virtiofs)
+
+target_sources(app PRIVATE src/main.c)

samples/subsys/fs/virtiofs/README.rst

@@ -0,0 +1,73 @@
+.. zephyr:code-sample:: virtiofs
+   :name: virtiofs filesystem
+   :relevant-api: file_system_api
+
+   Use file system API over virtiofs.
+
+Overview
+********
+
+This sample app demonstrates the use of Zephyr's :ref:`file system API
+<file_system_api>` over `virtiofs <https://virtio-fs.gitlab.io/>`_ by reading, creating and listing files and directories.
+In the case of virtiofs the mounted filesystem is a directory on the host.
+
+Requirements
+************
+This sample requires `virtiofsd <https://gitlab.com/virtio-fs/virtiofsd>`_ to run.
+
+Building
+********
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/fs/virtiofs
+   :board: qemu_x86_64
+   :goals: build
+   :compact:
+
+
+Running
+*******
+Before launching QEMU ``virtiofsd`` has to be running. QEMU's arguments are embedded using :code:`CONFIG_QEMU_EXTRA_FLAGS` and socket path is set to :code:`/tmp/vhostqemu`, so ``virtiofsd`` has to be launched using
+
+.. code-block::
+
+   virtiofsd --socket-path=/tmp/vhostqemu -o source=shared_dir_path
+
+where :code:`shared_dir_path` is a directory that will be mounted on Zephyr side.
+Then you can launch QEMU using:
+
+.. code-block::
+
+   west build -t run
+
+This sample will list the files and directories in the mounted filesystem and print the contents of the file :code:`file` in the mounted directory.
+This sample will also create some files and directories.
+You can create the sample directory using :code:`prepare_sample_directory.sh`.
+
+Example output:
+
+.. code-block::
+
+   *** Booting Zephyr OS build v4.1.0-rc1-28-gc6816316fc50 ***
+   /virtiofs directory tree:
+   - dir2 (type=dir)
+     - b (type=file, size=3)
+     - a (type=file, size=2)
+     - c (type=file, size=4)
+   - dir (type=dir)
+     - some_file (type=file, size=0)
+     - nested_dir (type=dir)
+        - some_other_file (type=file, size=0)
+   - file (type=file, size=27)
+
+   /virtiofs/file content:
+   this is a file on the host
+
+
+After running the sample you can check the created files:
+
+.. code-block:: console
+
+   shared_dir_path$ cat file_created_by_zephyr
+   hello world
+   shared_dir_path$ cat second_file_created_by_zephyr
+   lorem ipsum

samples/subsys/fs/virtiofs/boards/qemu_x86.overlay

@@ -0,0 +1,13 @@
+&pcie0 {
+	virtio_pci: virtio_pci {
+		compatible = "virtio,pci";
+
+		vendor-id = <0x1af4>;
+		device-id = <0x105a>;
+
+		interrupts = <0xb 0x0 0x0>;
+		interrupt-parent = <&intc>;
+
+		status = "okay";
+	};
+};

samples/subsys/fs/virtiofs/boards/qemu_x86_64.overlay

@@ -0,0 +1,13 @@
+&pcie0 {
+	virtio_pci: virtio_pci {
+		compatible = "virtio,pci";
+
+		vendor-id = <0x1af4>;
+		device-id = <0x105a>;
+
+		interrupts = <0xb 0x0 0x0>;
+		interrupt-parent = <&intc>;
+
+		status = "okay";
+	};
+};

samples/subsys/fs/virtiofs/prepare_sample_directory.sh

@@ -0,0 +1,11 @@
+# Copyright (c) 2025 Antmicro <www.antmicro.com>
+# SPDX-License-Identifier: Apache-2.0
+
+mkdir -p dir/nested_dir
+touch dir/some_file
+touch dir/nested_dir/some_other_file
+mkdir dir2
+echo "a" > dir2/a
+echo "bb" > dir2/b
+echo "ccc" > dir2/c
+echo "this is a file on the host" > file

samples/subsys/fs/virtiofs/prj.conf

@@ -0,0 +1,7 @@
+CONFIG_VIRTIO=y
+CONFIG_PCIE=y
+CONFIG_FILE_SYSTEM=y
+CONFIG_FILE_SYSTEM_VIRTIOFS=y
+CONFIG_HEAP_MEM_POOL_SIZE=100000
+CONFIG_MAIN_STACK_SIZE=16384
+CONFIG_QEMU_EXTRA_FLAGS="-chardev socket,id=char0,path=/tmp/vhostqemu -device vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs -m 32M -object memory-backend-memfd,id=mem,size=32M,share=on -numa node,memdev=mem"

samples/subsys/fs/virtiofs/sample.yaml

@@ -0,0 +1,10 @@
+sample:
+  name: virtio filesystem sample
+common:
+  tags:
+    - filesystem
+    - virtio
+tests:
+  sample.filesystem.virtiofs:
+    build_only: true
+    filter: CONFIG_DT_HAS_VIRTIO_PCI_ENABLED

samples/subsys/fs/virtiofs/src/main.c

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2025 Antmicro <www.antmicro.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <zephyr/device.h>
+#include <zephyr/fs/fs.h>
+#include <zephyr/fs/virtiofs.h>
+#include <zephyr/kernel.h>
+
+#define VIRTIO_DEV DEVICE_DT_GET(DT_NODELABEL(virtio_pci))
+
+#define MOUNT_POINT "/virtiofs"
+
+struct virtiofs_fs_data fs_data;
+
+static struct fs_mount_t mp = {
+	.type = FS_VIRTIOFS,
+	.fs_data = &fs_data,
+	.flags = 0,
+	.storage_dev = (void *)VIRTIO_DEV,
+	.mnt_point = MOUNT_POINT,
+};
+
+void dirtree(const char *path, int indent)
+{
+	struct fs_dir_t dir;
+
+	fs_dir_t_init(&dir);
+	if (fs_opendir(&dir, path) == 0) {
+		while (1) {
+			struct fs_dirent entry;
+
+			if (fs_readdir(&dir, &entry) == 0) {
+				if (entry.name[0] == '\0') {
+					break;
+				}
+				if (entry.type == FS_DIR_ENTRY_DIR) {
+					printf("%*s- %s (type=dir)\n", indent * 2, "", entry.name);
+					char *subdir_path = k_malloc(
+						strlen(path) + strlen(entry.name) + 2
+					);
+
+					if (subdir_path == NULL) {
+						printf("failed to allocate subdir path\n");
+						continue;
+					}
+					strcpy(subdir_path, path);
+					strcat(subdir_path, "/");
+					strcat(subdir_path, entry.name);
+					dirtree(subdir_path, indent + 1);
+					k_free(subdir_path);
+				} else {
+					printf(
+						"%*s- %s (type=file, size=%zu)\n",
+						indent * 2, "", entry.name, entry.size
+					);
+				}
+			} else {
+				printf("failed to readdir %s\n", path);
+				break;
+			}
+		};
+
+		fs_closedir(&dir);
+	} else {
+		printf("failed to opendir %s\n", path);
+	}
+}
+
+void create_file(const char *path, const char *content)
+{
+	struct fs_file_t file;
+
+	fs_file_t_init(&file);
+	if (fs_open(&file, path, FS_O_CREATE | FS_O_WRITE) == 0) {
+		fs_write(&file, content, strlen(content) + 1);
+	} else {
+		printf("failed to create %s\n", path);
+	}
+	fs_close(&file);
+}
+
+void print_file(const char *path)
+{
+	struct fs_file_t file;
+
+	fs_file_t_init(&file);
+	if (fs_open(&file, path, FS_O_READ) == 0) {
+		char buf[256] = "\0";
+		int read_c = fs_read(&file, buf, sizeof(buf));
+
+		if (read_c >= 0) {
+			buf[read_c] = 0;
+
+			printf(
+				"%s content:\n"
+				"%s\n",
+				path, buf
+			);
+		} else {
+			printf("failed to read from %s\n", path);
+		}
+
+		fs_close(&file);
+	} else {
+		printf("failed to open %s\n", path);
+	}
+}
+
+int main(void)
+{
+	if (fs_mount(&mp) == 0) {
+		printf("%s directory tree:\n", MOUNT_POINT);
+		dirtree(MOUNT_POINT, 0);
+		printf("\n");
+
+		print_file(MOUNT_POINT"/file");
+
+		create_file("/virtiofs/file_created_by_zephyr", "hello world\n");
+
+		create_file("/virtiofs/second_file_created_by_zephyr", "lorem ipsum\n");
+
+		fs_mkdir("/virtiofs/dir_created_by_zephyr");
+	} else {
+		printf("failed to mount %s\n", MOUNT_POINT);
+	}
+
+	return 0;
+}

subsys/fs/CMakeLists.txt

@@ -17,12 +17,16 @@ if(CONFIG_FILE_SYSTEM_LIB_LINK)
   endif()
 
   add_subdirectory_ifdef(CONFIG_FILE_SYSTEM_EXT2 ext2)
+  add_subdirectory_ifdef(CONFIG_FUSE_CLIENT fuse_client)
+  add_subdirectory_ifdef(CONFIG_FILE_SYSTEM_VIRTIOFS virtiofs)
 
   zephyr_library_link_libraries(FS)
 
   target_link_libraries_ifdef(CONFIG_FAT_FILESYSTEM_ELM   FS INTERFACE ELMFAT)
   target_link_libraries_ifdef(CONFIG_FILE_SYSTEM_LITTLEFS FS INTERFACE LITTLEFS)
   target_link_libraries_ifdef(CONFIG_FILE_SYSTEM_EXT2     FS INTERFACE EXT2)
+  target_link_libraries_ifdef(CONFIG_FUSE_CLIENT          FS INTERFACE FUSE_CLIENT)
+  target_link_libraries_ifdef(CONFIG_FILE_SYSTEM_VIRTIOFS FS INTERFACE VIRTIOFS)
 endif()
 
 add_subdirectory_ifdef(CONFIG_FCB  ./fcb)