Lguest support for Virtio

	bool "Lguest guest support"

	select PARAVIRT

	depends on !X86_PAE

	select VIRTIO

	select VIRTIO_RING

	select VIRTIO_CONSOLE

	help

	  Lguest is a tiny in-kernel hypervisor.  Selecting this will

	  allow your kernel to boot under lguest.  This option will increase

	  your kernel size by about 6k.  If in doubt, say N.

	  If you say Y here, make sure you say Y (or M) to the virtio block

	  and net drivers which lguest needs.

#include <linux/clockchips.h>

#include <linux/lguest.h>

#include <linux/lguest_launcher.h>

#include <linux/virtio_console.h>

#include <asm/paravirt.h>

#include <asm/param.h>

#include <asm/page.h>

	return "LGUEST";

}

/* Before virtqueues are set up, we use LHCALL_NOTIFY on normal memory to

 * produce console output. */

static __init int early_put_chars(u32 vtermno, const char *buf, int count)

{

	char scratch[17];

	unsigned int len = count;

	if (len > sizeof(scratch) - 1)

		len = sizeof(scratch) - 1;

	scratch[len] = '\0';

	memcpy(scratch, buf, len);

	hcall(LHCALL_NOTIFY, __pa(scratch), 0, 0);

	/* This routine returns the number of bytes actually written. */

	return len;

}

/*G:050

 * Patching (Powerfully Placating Performance Pedants)

 *

	 * adapted for lguest's use. */

	add_preferred_console("hvc", 0, NULL);

	/* Register our very early console. */

	virtio_cons_early_init(early_put_chars);

	/* Last of all, we set the power management poweroff hook to point to

	 * the Guest routine to power off. */

	pm_power_off = lguest_power_off;

# Guest requires the device configuration and probing code.

obj-$(CONFIG_LGUEST_GUEST) += lguest_device.o

# Host requires the other files, which can be a module.

obj-$(CONFIG_LGUEST)	+= lg.o

lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \

/*P:050 Lguest guests use a very simple method to describe devices.  It's a

 * series of device descriptors contained just above the top of normal

 * memory.

 *

 * We use the standard "virtio" device infrastructure, which provides us with a

 * console, a network and a block driver.  Each one expects some configuration

 * information and a "virtqueue" mechanism to send and receive data. :*/

#include <linux/init.h>

#include <linux/bootmem.h>

#include <linux/lguest_launcher.h>

#include <linux/virtio.h>

#include <linux/virtio_config.h>

#include <linux/interrupt.h>

#include <linux/virtio_ring.h>

#include <linux/err.h>

#include <asm/io.h>

#include <asm/paravirt.h>

#include <asm/lguest_hcall.h>

/* The pointer to our (page) of device descriptions. */

static void *lguest_devices;

/* Unique numbering for lguest devices. */

static unsigned int dev_index;

/* For Guests, device memory can be used as normal memory, so we cast away the

 * __iomem to quieten sparse. */

static inline void *lguest_map(unsigned long phys_addr, unsigned long pages)

{

	return (__force void *)ioremap(phys_addr, PAGE_SIZE*pages);

}

static inline void lguest_unmap(void *addr)

{

	iounmap((__force void __iomem *)addr);

}

/*D:100 Each lguest device is just a virtio device plus a pointer to its entry

 * in the lguest_devices page. */

struct lguest_device {

	struct virtio_device vdev;

	/* The entry in the lguest_devices page for this device. */

	struct lguest_device_desc *desc;

};

/* Since the virtio infrastructure hands us a pointer to the virtio_device all

 * the time, it helps to have a curt macro to get a pointer to the struct

 * lguest_device it's enclosed in.  */

#define to_lgdev(vdev) container_of(vdev, struct lguest_device, vdev)

/*D:130

 * Device configurations

 *

 * The configuration information for a device consists of a series of fields.

 * The device will look for these fields during setup.

 *

 * For us these fields come immediately after that device's descriptor in the

 * lguest_devices page.

 *

 * Each field starts with a "type" byte, a "length" byte, then that number of

 * bytes of configuration information.  The device descriptor tells us the

 * total configuration length so we know when we've reached the last field. */

/* type + length bytes */

#define FHDR_LEN 2

/* This finds the first field of a given type for a device's configuration. */

static void *lg_find(struct virtio_device *vdev, u8 type, unsigned int *len)

{

	struct lguest_device_desc *desc = to_lgdev(vdev)->desc;

	int i;

	for (i = 0; i < desc->config_len; i += FHDR_LEN + desc->config[i+1]) {

		if (desc->config[i] == type) {

			/* Mark it used, so Host can know we looked at it, and

			 * also so we won't find the same one twice. */

			desc->config[i] |= 0x80;

			/* Remember, the second byte is the length. */

			*len = desc->config[i+1];

			/* We return a pointer to the field header. */

			return desc->config + i;

		}

	}

	/* Not found: return NULL for failure. */

	return NULL;

}

/* Once they've found a field, getting a copy of it is easy. */

static void lg_get(struct virtio_device *vdev, void *token,

		   void *buf, unsigned len)

{

	/* Check they didn't ask for more than the length of the field! */

	BUG_ON(len > ((u8 *)token)[1]);

	memcpy(buf, token + FHDR_LEN, len);

}

/* Setting the contents is also trivial. */

static void lg_set(struct virtio_device *vdev, void *token,

		   const void *buf, unsigned len)

{

	BUG_ON(len > ((u8 *)token)[1]);

	memcpy(token + FHDR_LEN, buf, len);

}

/* The operations to get and set the status word just access the status field

 * of the device descriptor. */

static u8 lg_get_status(struct virtio_device *vdev)

{

	return to_lgdev(vdev)->desc->status;

}

static void lg_set_status(struct virtio_device *vdev, u8 status)

{

	to_lgdev(vdev)->desc->status = status;

}

/*

 * Virtqueues

 *

 * The other piece of infrastructure virtio needs is a "virtqueue": a way of

 * the Guest device registering buffers for the other side to read from or

 * write into (ie. send and receive buffers).  Each device can have multiple

 * virtqueues: for example the console has one queue for sending and one for

 * receiving.

 *

 * Fortunately for us, a very fast shared-memory-plus-descriptors virtqueue

 * already exists in virtio_ring.c.  We just need to connect it up.

 *

 * We start with the information we need to keep about each virtqueue.

 */

/*D:140 This is the information we remember about each virtqueue. */

struct lguest_vq_info

{

	/* A copy of the information contained in the device config. */

	struct lguest_vqconfig config;

	/* The address where we mapped the virtio ring, so we can unmap it. */

	void *pages;

};

/* When the virtio_ring code wants to prod the Host, it calls us here and we

 * make a hypercall.  We hand the page number of the virtqueue so the Host

 * knows which virtqueue we're talking about. */

static void lg_notify(struct virtqueue *vq)

{

	/* We store our virtqueue information in the "priv" pointer of the

	 * virtqueue structure. */

	struct lguest_vq_info *lvq = vq->priv;

	hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0);

}

/* This routine finds the first virtqueue described in the configuration of

 * this device and sets it up.

 *

 * This is kind of an ugly duckling.  It'd be nicer to have a standard

 * representation of a virtqueue in the configuration space, but it seems that

 * everyone wants to do it differently.  The KVM guys want the Guest to

 * allocate its own pages and tell the Host where they are, but for lguest it's

 * simpler for the Host to simply tell us where the pages are.

 *

 * So we provide devices with a "find virtqueue and set it up" function. */

static struct virtqueue *lg_find_vq(struct virtio_device *vdev,

				    bool (*callback)(struct virtqueue *vq))

{

	struct lguest_vq_info *lvq;

	struct virtqueue *vq;

	unsigned int len;

	void *token;

	int err;

	/* Look for a field of the correct type to mark a virtqueue.  Note that

	 * if this succeeds, then the type will be changed so it won't be found

	 * again, and future lg_find_vq() calls will find the next

	 * virtqueue (if any). */

	token = vdev->config->find(vdev, VIRTIO_CONFIG_F_VIRTQUEUE, &len);

	if (!token)

		return ERR_PTR(-ENOENT);

	lvq = kmalloc(sizeof(*lvq), GFP_KERNEL);

	if (!lvq)

		return ERR_PTR(-ENOMEM);

	/* Note: we could use a configuration space inside here, just like we

	 * do for the device.  This would allow expansion in future, because

	 * our configuration system is designed to be expansible.  But this is

	 * way easier. */

	if (len != sizeof(lvq->config)) {

		dev_err(&vdev->dev, "Unexpected virtio config len %u\n", len);

		err = -EIO;

		goto free_lvq;

	}

	/* Make a copy of the "struct lguest_vqconfig" field.  We need a copy

	 * because the config space might not be aligned correctly. */

	vdev->config->get(vdev, token, &lvq->config, sizeof(lvq->config));

	/* Figure out how many pages the ring will take, and map that memory */

	lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT,

				DIV_ROUND_UP(vring_size(lvq->config.num),

					     PAGE_SIZE));

	if (!lvq->pages) {

		err = -ENOMEM;

		goto free_lvq;

	}

	/* OK, tell virtio_ring.c to set up a virtqueue now we know its size

	 * and we've got a pointer to its pages. */

	vq = vring_new_virtqueue(lvq->config.num, vdev, lvq->pages,

				 lg_notify, callback);

	if (!vq) {

		err = -ENOMEM;

		goto unmap;

	}

	/* Tell the interrupt for this virtqueue to go to the virtio_ring

	 * interrupt handler. */

	/* FIXME: We used to have a flag for the Host to tell us we could use

	 * the interrupt as a source of randomness: it'd be nice to have that

	 * back.. */

	err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED,

			  vdev->dev.bus_id, vq);

	if (err)

		goto destroy_vring;

	/* Last of all we hook up our 'struct lguest_vq_info" to the

	 * virtqueue's priv pointer. */

	vq->priv = lvq;

	return vq;

destroy_vring:

	vring_del_virtqueue(vq);

unmap:

	lguest_unmap(lvq->pages);

free_lvq:

	kfree(lvq);

	return ERR_PTR(err);

}

/*:*/

/* Cleaning up a virtqueue is easy */

static void lg_del_vq(struct virtqueue *vq)

{

	struct lguest_vq_info *lvq = vq->priv;

	/* Tell virtio_ring.c to free the virtqueue. */

	vring_del_virtqueue(vq);

	/* Unmap the pages containing the ring. */

	lguest_unmap(lvq->pages);

	/* Free our own queue information. */

	kfree(lvq);

}

/* The ops structure which hooks everything together. */

static struct virtio_config_ops lguest_config_ops = {

	.find = lg_find,

	.get = lg_get,

	.set = lg_set,

	.get_status = lg_get_status,

	.set_status = lg_set_status,

	.find_vq = lg_find_vq,

	.del_vq = lg_del_vq,

};

/* The root device for the lguest virtio devices.  This makes them appear as

 * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */

static struct device lguest_root = {

	.parent = NULL,

	.bus_id = "lguest",

};

/*D:120 This is the core of the lguest bus: actually adding a new device.

 * It's a separate function because it's neater that way, and because an

 * earlier version of the code supported hotplug and unplug.  They were removed

 * early on because they were never used.

 *

 * As Andrew Tridgell says, "Untested code is buggy code".

 *

 * It's worth reading this carefully: we start with a pointer to the new device

 * descriptor in the "lguest_devices" page. */

static void add_lguest_device(struct lguest_device_desc *d)

{

	struct lguest_device *ldev;

	ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);

	if (!ldev) {

		printk(KERN_EMERG "Cannot allocate lguest dev %u\n",

		       dev_index++);

		return;

	}

	/* This devices' parent is the lguest/ dir. */

	ldev->vdev.dev.parent = &lguest_root;

	/* We have a unique device index thanks to the dev_index counter. */

	ldev->vdev.index = dev_index++;

	/* The device type comes straight from the descriptor.  There's also a

	 * device vendor field in the virtio_device struct, which we leave as

	 * 0. */

	ldev->vdev.id.device = d->type;

	/* We have a simple set of routines for querying the device's

	 * configuration information and setting its status. */

	ldev->vdev.config = &lguest_config_ops;

	/* And we remember the device's descriptor for lguest_config_ops. */

	ldev->desc = d;

	/* register_virtio_device() sets up the generic fields for the struct

	 * virtio_device and calls device_register().  This makes the bus

	 * infrastructure look for a matching driver. */

	if (register_virtio_device(&ldev->vdev) != 0) {

		printk(KERN_ERR "Failed to register lguest device %u\n",

		       ldev->vdev.index);

		kfree(ldev);

	}

}

/*D:110 scan_devices() simply iterates through the device page.  The type 0 is

 * reserved to mean "end of devices". */

static void scan_devices(void)

{

	unsigned int i;

	struct lguest_device_desc *d;

	/* We start at the page beginning, and skip over each entry. */

	for (i = 0; i < PAGE_SIZE; i += sizeof(*d) + d->config_len) {

		d = lguest_devices + i;

		/* Once we hit a zero, stop. */

		if (d->type == 0)

			break;

		add_lguest_device(d);

	}

}

/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the

 * lguest device infrastructure.  We check that we are a Guest by checking

 * pv_info.name: there are other ways of checking, but this seems most

 * obvious to me.

 *

 * So we can access the "struct lguest_device_desc"s easily, we map that memory

 * and store the pointer in the global "lguest_devices".  Then we register a

 * root device from which all our devices will hang (this seems to be the

 * correct sysfs incantation).

 *

 * Finally we call scan_devices() which adds all the devices found in the

 * lguest_devices page. */

static int __init lguest_devices_init(void)

{

	if (strcmp(pv_info.name, "lguest") != 0)

		return 0;

	if (device_register(&lguest_root) != 0)

		panic("Could not register lguest root");

	/* Devices are in a single page above top of "normal" mem */

	lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1);

	scan_devices();

	return 0;

}

/* We do this after core stuff, but before the drivers. */

postcore_initcall(lguest_devices_init);

/*D:150 At this point in the journey we used to now wade through the lguest

 * devices themselves: net, block and console.  Since they're all now virtio

 * devices rather than lguest-specific, I've decided to ignore them.  Mostly,

 * they're kind of boring.  But this does mean you'll never experience the

 * thrill of reading the forbidden love scene buried deep in the block driver.

 *

 * "make Launcher" beckons, where we answer questions like "Where do Guests

 * come from?", and "What do you do when someone asks for optimization?". */

 * complex burden for the Host and suboptimal for the Guest, so we have our own

 * "lguest" bus and simple drivers.

 *

 * Devices are described by an array of LGUEST_MAX_DEVICES of these structs,

 * placed by the Launcher just above the top of physical memory:

 * Devices are described by a simplified ID, a status byte, and some "config"

 * bytes which describe this device's configuration.  This is placed by the

 * Launcher just above the top of physical memory:

 */

struct lguest_device_desc {

	/* The device type: console, network, disk etc. */

	__u16 type;

#define LGUEST_DEVICE_T_CONSOLE	1

#define LGUEST_DEVICE_T_NET	2

#define LGUEST_DEVICE_T_BLOCK	3

	/* The specific features of this device: these depends on device type

	 * except for LGUEST_DEVICE_F_RANDOMNESS. */

	__u16 features;

#define LGUEST_NET_F_NOCSUM		0x4000 /* Don't bother checksumming */

#define LGUEST_DEVICE_F_RANDOMNESS	0x8000 /* IRQ is fairly random */

	/* This is how the Guest reports status of the device: the Host can set

	 * LGUEST_DEVICE_S_REMOVED to indicate removal, but the rest are only

	 * ever manipulated by the Guest, and only ever set. */

	__u16 status;

/* 256 and above are device specific. */

#define LGUEST_DEVICE_S_ACKNOWLEDGE	1 /* We have seen device. */

#define LGUEST_DEVICE_S_DRIVER		2 /* We have found a driver */

#define LGUEST_DEVICE_S_DRIVER_OK	4 /* Driver says OK! */

#define LGUEST_DEVICE_S_REMOVED		8 /* Device has gone away. */

#define LGUEST_DEVICE_S_REMOVED_ACK	16 /* Driver has been told. */

#define LGUEST_DEVICE_S_FAILED		128 /* Something actually failed */

	/* The device type: console, network, disk etc.  Type 0 terminates. */

	__u8 type;

	/* The number of bytes of the config array. */

	__u8 config_len;

	/* A status byte, written by the Guest. */

	__u8 status;

	__u8 config[0];

};

	/* Each device exists somewhere in Guest physical memory, over some

	 * number of pages. */

	__u16 num_pages;

/*D:135 This is how we expect the device configuration field for a virtqueue

 * (type VIRTIO_CONFIG_F_VIRTQUEUE) to be laid out: */

struct lguest_vqconfig {

	/* The number of entries in the virtio_ring */

	__u16 num;

	/* The interrupt we get when something happens. */

	__u16 irq;

	/* The page number of the virtio ring for this device. */

	__u32 pfn;

};

/*:*/