diff options
| -rw-r--r-- | arch/x86/lguest/Kconfig | 5 | ||||
| -rw-r--r-- | arch/x86/lguest/boot.c | 21 | ||||
| -rw-r--r-- | drivers/lguest/Makefile | 3 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 373 | ||||
| -rw-r--r-- | include/linux/lguest_launcher.h | 47 |
5 files changed, 421 insertions, 28 deletions
diff --git a/arch/x86/lguest/Kconfig b/arch/x86/lguest/Kconfig index 44dccfd845f8..c4dffbeea5e1 100644 --- a/arch/x86/lguest/Kconfig +++ b/arch/x86/lguest/Kconfig @@ -2,8 +2,13 @@ config LGUEST_GUEST 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. diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 959aeebb02f5..495e46a1f111 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -55,6 +55,7 @@ #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> @@ -849,6 +850,23 @@ static __init char *lguest_memory_setup(void) 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) * @@ -1048,6 +1066,9 @@ __init void lguest_init(void *boot) * 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; diff --git a/drivers/lguest/Makefile b/drivers/lguest/Makefile index a63f75dc41a1..5e8272d296d8 100644 --- a/drivers/lguest/Makefile +++ b/drivers/lguest/Makefile @@ -1,3 +1,6 @@ +# 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 \ diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c new file mode 100644 index 000000000000..71c64837b437 --- /dev/null +++ b/drivers/lguest/lguest_device.c @@ -0,0 +1,373 @@ +/*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?". */ diff --git a/include/linux/lguest_launcher.h b/include/linux/lguest_launcher.h index 5ec04a225e4f..61e1e3e6b1cc 100644 --- a/include/linux/lguest_launcher.h +++ b/include/linux/lguest_launcher.h @@ -22,37 +22,28 @@ * 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; }; /*:*/ |