user/vmm/include/vmm/virtio.h

/*
 * Copyright (c) 2016 Google Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

 #pragma once

#include <stdint.h>
#include <err.h>
#include <sys/uio.h>
#include <vmm/virtio_ring.h>
#include <vmm/sched.h>

// This file contains the core virtio structs, functions, and macros for Akaros

// Print errors caused by incorrect driver behavior
#define VIRTIO_DRI_ERRX(dev, fmt, ...) \
	errx(1, "\n  %s:%d\n  Virtio Device: %s: Error, driver behavior.\n  "\
		fmt, __FILE__, __LINE__, (dev)->name, ## __VA_ARGS__)

// Print warnings caused by incorrect driver behavior
#define VIRTIO_DRI_WARNX(dev, fmt, ...) \
	warnx("\n  %s:%d\n  Virtio Device: %s: Warning, driver behavior.\n  "\
		fmt, __FILE__, __LINE__, (dev)->name, ## __VA_ARGS__)

// Print errors caused by incorrect device behavior
#define VIRTIO_DEV_ERRX(dev, fmt, ...) \
	errx(1, "\n  %s:%d\n  Virtio Device: %s: Error, device behavior.\n  "\
		fmt, __FILE__, __LINE__, (dev)->name, ## __VA_ARGS__)

// Print warnings caused by incorrect device behavior
#define VIRTIO_DEV_WARNX(dev, fmt, ...) \
	warnx("\n  %s:%d\n  Virtio Device: %s: Warning, device behavior.\n  "\
		fmt, __FILE__, __LINE__, (dev)->name, ## __VA_ARGS__)



struct virtio_vq {
	// The name of the vq e.g. for printing errors
	char *name;

	// The vqdev that contains this vq
	struct virtio_vq_dev *vqdev;

	// The vring contains pointers to the descriptor table and available and
	// used rings as well as the number of elements in the queue.
	struct vring vring;

	// The maximum number of elements in the queue that the device is ready to
	// process. Reads from the register corresponding to this value return 0x0
	// if the queue is not available. A queue's size is always a power of 2.
	int qnum_max;

	// The driver writes 0x1 to qready to tell the device
	// that it can execute requests from this vq
	uint32_t qready;

	// The last vq.vring.avail->idx that the service function saw while
	// processing the queue
	uint16_t last_avail;

	// The service function that processes buffers for this queue
	void *(*srv_fn)(void *arg);

	// The thread that the service function is running in
	struct task_thread *srv_th;

	// Write eventfd to wake up the service function; it blocks on eventfd read
	int eventfd;
};

struct virtio_vq_dev {
	// The name of the device e.g. for printing errors
	char *name;

	// The type of the device e.g. VIRTIO_ID_CONSOLE for a console device
	uint32_t dev_id;

	// The features supported by this device
	uint64_t dev_feat;

	// The features supported by the driver (these are set by the guest)
	uint64_t dri_feat;

	// The number of virtio_vqs on the device
	uint32_t num_vqs;

	// A pointer to the device-specific config space
	void *cfg;

	// A pointer to a default device-specific config space
	// If set, cfg_sz bytes, starting at cfg_d, will be
	// copied to cfg.
	void *cfg_d;

	// The size, in bytes, of the device-specific config space
	// Used by the device to bounds-check driver access
	uint64_t cfg_sz;

	// The virtio transport dev that contains this vqdev
	// i.e. struct virtio_mmio_dev
	void *transport_dev;

	// Flexible array of vqs on this device
	struct virtio_vq vqs[];
};

// Do not include virtio_lguest_helpers.h directly. You should include the
// contained functions by including virtio.h. These functions are kept apart
// from virtio.h so that we can keep a clean separation between our code
// and code derived from lguest.
#include <vmm/virtio_lguest_helpers.h>

// Returns NULL if the features are valid, otherwise returns
// an error string describing what part of validation failed
// We pass the vqdev instead of just the dev_id in case we
// also want to validate the device-specific config space.
// feat is the feature vector that you want to validate for the vqdev
const char *virtio_validate_feat(struct virtio_vq_dev *vqdev, uint64_t feat);