virtio: add API for VIRTIO devices and add VIRTIO PCI driver

This commit adds the API for accessing VIRTIO devices, and adds a driver
for a VIRTIO PCIE device based on the newly added API.

This commit is based on the Virtual I/O Device (VIRTIO) Version 1.3
specification:
https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.pdf

Signed-off-by: Jakub Michalski <jmichalski@antmicro.com>
Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>

Author: jmichalski-ant

MAINTAINERS.yml

@@ -2176,6 +2176,20 @@ Release Notes:
   tests:
     - drivers.video
 
+"Drivers: VIRTIO":
+  status: maintained
+  maintainers:
+    - fkokosinski
+    - tgorochowik
+  collaborators:
+    - kgugala
+  files:
+    - drivers/virtio/
+    - dts/bindings/virtio/
+    - include/zephyr/virtio/
+  labels:
+    - "area: VIRTIO"
+
 "Drivers: W1":
   status: maintained
   maintainers:

drivers/CMakeLists.txt

@@ -89,6 +89,7 @@ add_subdirectory_ifdef(CONFIG_SYSCON syscon)
 add_subdirectory_ifdef(CONFIG_SYS_CLOCK_EXISTS timer)
 add_subdirectory_ifdef(CONFIG_TEE tee)
 add_subdirectory_ifdef(CONFIG_VIDEO video)
+add_subdirectory_ifdef(CONFIG_VIRTIO virtio)
 add_subdirectory_ifdef(CONFIG_VIRTUALIZATION virtualization)
 add_subdirectory_ifdef(CONFIG_W1 w1)
 add_subdirectory_ifdef(CONFIG_WATCHDOG watchdog)

drivers/Kconfig

@@ -88,6 +88,7 @@ source "drivers/timer/Kconfig"
 source "drivers/usb/Kconfig"
 source "drivers/usb_c/Kconfig"
 source "drivers/video/Kconfig"
+source "drivers/virtio/Kconfig"
 source "drivers/virtualization/Kconfig"
 source "drivers/w1/Kconfig"
 source "drivers/watchdog/Kconfig"

drivers/virtio/CMakeLists.txt

@@ -0,0 +1,7 @@
+# Copyright (c) 2024 Antmicro <www.antmicro.com>
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_sources_ifdef(CONFIG_VIRTIO virtqueue.c virtio_common.c)
+zephyr_library_sources_ifdef(CONFIG_VIRTIO_PCI virtio_pci.c)

drivers/virtio/Kconfig

@@ -0,0 +1,22 @@
+# Copyright (c) 2024 Antmicro <www.antmicro.com>
+# SPDX-License-Identifier: Apache-2.0
+
+config VIRTIO
+	bool "support for VIRTIO"
+	help
+	  Enable options for VIRTIO
+
+if VIRTIO
+
+config VIRTIO_PCI
+	bool "support for VIRTIO over PCI"
+	default y
+	depends on DT_HAS_VIRTIO_PCI_ENABLED
+	help
+	  Enable options for VIRTIO over PCI
+
+endif # VIRTIO
+
+module = VIRTIO
+module-str = VIRTIO
+source "subsys/logging/Kconfig.template.log_config"

drivers/virtio/virtio_common.c

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Antmicro <www.antmicro.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/byteorder.h>
+#include <zephyr/virtio/virtio.h>
+#include <zephyr/virtio/virtqueue.h>
+#include "virtio_common.h"
+
+LOG_MODULE_REGISTER(virtio_common, CONFIG_VIRTIO_LOG_LEVEL);
+
+void virtio_isr(const struct device *dev, uint8_t isr_status, uint16_t virtqueue_count)
+{
+	if (isr_status & VIRTIO_QUEUE_INTERRUPT) {
+		for (int i = 0; i < virtqueue_count; i++) {
+			struct virtq *vq = virtio_get_virtqueue(dev, i);
+			uint16_t used_idx = sys_le16_to_cpu(vq->used->idx);
+
+			while (vq->last_used_idx != used_idx) {
+				uint16_t idx = vq->last_used_idx % vq->num;
+				uint16_t idx_le = sys_cpu_to_le16(idx);
+				uint16_t chain_head_le = vq->used->ring[idx_le].id;
+				uint16_t chain_head = sys_le16_to_cpu(chain_head_le);
+				uint32_t used_len = sys_le32_to_cpu(
+					vq->used->ring[idx_le].len
+				);
+
+				/*
+				 * We are making a copy here, because chain will be
+				 * returned before invoking the callback and may be
+				 * overwritten by the time callback is called. This
+				 * is to allow callback to immediately place the
+				 * descriptors back in the avail_ring
+				 */
+				struct virtq_receive_callback_entry cbe =
+					vq->recv_cbs[chain_head];
+
+				uint16_t next = chain_head;
+				bool last = false;
+
+				/*
+				 * We are done processing the descriptor chain, and
+				 * we can add used descriptors back to the free stack.
+				 * The only thing left to do is calling the callback
+				 * associated with the chain, but it was saved above on
+				 * the stack, so other code is free to use the descriptors
+				 */
+				while (!last) {
+					uint16_t curr = next;
+					uint16_t curr_le = sys_cpu_to_le16(curr);
+
+					next = vq->desc[curr_le].next;
+					last = !(vq->desc[curr_le].flags & VIRTQ_DESC_F_NEXT);
+					virtq_add_free_desc(vq, curr);
+				}
+
+				vq->last_used_idx++;
+
+				if (cbe.cb) {
+					cbe.cb(cbe.opaque, used_len);
+				}
+			}
+		}
+	}
+	if (isr_status & VIRTIO_DEVICE_CONFIGURATION_INTERRUPT) {
+		LOG_ERR("device configuration change interrupt is currently unsupported");
+	}
+}

drivers/virtio/virtio_common.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2025 Antmicro <www.antmicro.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_VIRTIO_VIRTIO_COMMON_H_
+#define ZEPHYR_VIRTIO_VIRTIO_COMMON_H_
+
+#define DEVICE_STATUS_ACKNOWLEDGE 0
+#define DEVICE_STATUS_DRIVER      1
+#define DEVICE_STATUS_DRIVER_OK   2
+#define DEVICE_STATUS_FEATURES_OK 3
+#define DEVICE_STATUS_NEEDS_RESET 6
+#define DEVICE_STATUS_FAILED      7
+
+#define VIRTIO_F_VERSION_1 32
+
+/* Ranges of feature bits for specific device types (see spec 2.2)*/
+#define DEV_TYPE_FEAT_RANGE_0_BEGIN 0
+#define DEV_TYPE_FEAT_RANGE_0_END   23
+#define DEV_TYPE_FEAT_RANGE_1_BEGIN 50
+#define DEV_TYPE_FEAT_RANGE_1_END   127
+
+/*
+ * While defined separately in 4.1.4.5 for PCI and in 4.2.2 for MMIO
+ * the same bits are responsible for the same interrupts, so defines
+ * with them can be unified
+ */
+#define VIRTIO_QUEUE_INTERRUPT                1
+#define VIRTIO_DEVICE_CONFIGURATION_INTERRUPT 2
+
+
+/**
+ * Common virtio isr
+ *
+ * @param dev virtio device it operates on
+ * @param isr_status value of isr status register
+ * @param virtqueue_count amount of available virtqueues
+ */
+void virtio_isr(const struct device *dev, uint8_t isr_status, uint16_t virtqueue_count);
+
+#endif /*ZEPHYR_VIRTIO_VIRTIO_COMMON_H_*/