mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
![Rusty Russell](/assets/img/avatar_default.png)
A reset function solves three problems: 1) It allows us to renegotiate features, eg. if we want to upgrade a guest driver without rebooting the guest. 2) It gives us a clean way of shutting down virtqueues: after a reset, we know that the buffers won't be used by the host, and 3) It helps the guest recover from messed-up drivers. So we remove the ->shutdown hook, and the only way we now remove feature bits is via reset. We leave it to the driver to do the reset before it deletes queues: the balloon driver, for example, needs to chat to the host in its remove function. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
407 lines
13 KiB
C
407 lines
13 KiB
C
/*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 one or more
|
|
* virtqueues, a feature bitmaks, and some configuration bytes. The
|
|
* configuration bytes don't really matter to us: the Launcher sets them up, and
|
|
* the driver will look at them during setup.
|
|
*
|
|
* A convenient routine to return the device's virtqueue config array:
|
|
* immediately after the descriptor. */
|
|
static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc)
|
|
{
|
|
return (void *)(desc + 1);
|
|
}
|
|
|
|
/* The features come immediately after the virtqueues. */
|
|
static u8 *lg_features(const struct lguest_device_desc *desc)
|
|
{
|
|
return (void *)(lg_vq(desc) + desc->num_vq);
|
|
}
|
|
|
|
/* The config space comes after the two feature bitmasks. */
|
|
static u8 *lg_config(const struct lguest_device_desc *desc)
|
|
{
|
|
return lg_features(desc) + desc->feature_len * 2;
|
|
}
|
|
|
|
/* The total size of the config page used by this device (incl. desc) */
|
|
static unsigned desc_size(const struct lguest_device_desc *desc)
|
|
{
|
|
return sizeof(*desc)
|
|
+ desc->num_vq * sizeof(struct lguest_vqconfig)
|
|
+ desc->feature_len * 2
|
|
+ desc->config_len;
|
|
}
|
|
|
|
/* This tests (and acknowleges) a feature bit. */
|
|
static bool lg_feature(struct virtio_device *vdev, unsigned fbit)
|
|
{
|
|
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
|
|
u8 *features;
|
|
|
|
/* Obviously if they ask for a feature off the end of our feature
|
|
* bitmap, it's not set. */
|
|
if (fbit / 8 > desc->feature_len)
|
|
return false;
|
|
|
|
/* The feature bitmap comes after the virtqueues. */
|
|
features = lg_features(desc);
|
|
if (!(features[fbit / 8] & (1 << (fbit % 8))))
|
|
return false;
|
|
|
|
/* We set the matching bit in the other half of the bitmap to tell the
|
|
* Host we want to use this feature. We don't use this yet, but we
|
|
* could in future. */
|
|
features[desc->feature_len + fbit / 8] |= (1 << (fbit % 8));
|
|
return true;
|
|
}
|
|
|
|
/* Once they've found a field, getting a copy of it is easy. */
|
|
static void lg_get(struct virtio_device *vdev, unsigned int offset,
|
|
void *buf, unsigned len)
|
|
{
|
|
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
|
|
|
|
/* Check they didn't ask for more than the length of the config! */
|
|
BUG_ON(offset + len > desc->config_len);
|
|
memcpy(buf, lg_config(desc) + offset, len);
|
|
}
|
|
|
|
/* Setting the contents is also trivial. */
|
|
static void lg_set(struct virtio_device *vdev, unsigned int offset,
|
|
const void *buf, unsigned len)
|
|
{
|
|
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
|
|
|
|
/* Check they didn't ask for more than the length of the config! */
|
|
BUG_ON(offset + len > desc->config_len);
|
|
memcpy(lg_config(desc) + offset, 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)
|
|
{
|
|
BUG_ON(!status);
|
|
to_lgdev(vdev)->desc->status = status;
|
|
}
|
|
|
|
/* To reset the device, we (ab)use the NOTIFY hypercall, with the descriptor
|
|
* address of the device. The Host will zero the status and all the
|
|
* features. */
|
|
static void lg_reset(struct virtio_device *vdev)
|
|
{
|
|
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
|
|
|
|
hcall(LHCALL_NOTIFY, (max_pfn<<PAGE_SHIFT) + offset, 0, 0);
|
|
}
|
|
|
|
/*
|
|
* 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 driver uses one queue for sending and
|
|
* another 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 coders 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,
|
|
unsigned index,
|
|
void (*callback)(struct virtqueue *vq))
|
|
{
|
|
struct lguest_device *ldev = to_lgdev(vdev);
|
|
struct lguest_vq_info *lvq;
|
|
struct virtqueue *vq;
|
|
int err;
|
|
|
|
/* We must have this many virtqueues. */
|
|
if (index >= ldev->desc->num_vq)
|
|
return ERR_PTR(-ENOENT);
|
|
|
|
lvq = kmalloc(sizeof(*lvq), GFP_KERNEL);
|
|
if (!lvq)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
/* Make a copy of the "struct lguest_vqconfig" entry, which sits after
|
|
* the descriptor. We need a copy because the config space might not
|
|
* be aligned correctly. */
|
|
memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config));
|
|
|
|
printk("Mapping virtqueue %i addr %lx\n", index,
|
|
(unsigned long)lvq->config.pfn << PAGE_SHIFT);
|
|
/* 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),
|
|
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;
|
|
|
|
/* Release the interrupt */
|
|
free_irq(lvq->config.irq, vq);
|
|
/* 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 = {
|
|
.feature = lg_feature,
|
|
.get = lg_get,
|
|
.set = lg_set,
|
|
.get_status = lg_get_status,
|
|
.set_status = lg_set_status,
|
|
.reset = lg_reset,
|
|
.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;
|
|
|
|
/* Start with zeroed memory; Linux's device layer seems to count on
|
|
* it. */
|
|
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 += desc_size(d)) {
|
|
d = lguest_devices + i;
|
|
|
|
/* Once we hit a zero, stop. */
|
|
if (d->type == 0)
|
|
break;
|
|
|
|
printk("Device at %i has size %u\n", i, desc_size(d));
|
|
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?". */
|