Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=19f1537b7b8a9a82665db3ad8210a9d954d13acd
Commit: 19f1537b7b8a9a82665db3ad8210a9d954d13acd
Parent: 15045275c32bf6d15d32c2eca8157be9c0ba6e45
Author: Rusty Russell <[EMAIL PROTECTED]>
AuthorDate: Mon Oct 22 11:24:21 2007 +1000
Committer: Rusty Russell <[EMAIL PROTECTED]>
CommitDate: Tue Oct 23 15:49:56 2007 +1000
Lguest support for Virtio
This makes lguest able to use the virtio devices.
We change the device descriptor page from a simple array to a variable
length "type, config_len, status, config data..." format, and
implement virtio_config_ops to read from that config data.
We use the virtio ring implementation for an efficient Guest <-> Host
virtqueue mechanism, and the new LHCALL_NOTIFY hypercall to kick the
host when it changes.
We also use LHCALL_NOTIFY on kernel addresses for very very early
console output. We could have another hypercall, but this hack works
quite well.
Signed-off-by: Rusty Russell <[EMAIL PROTECTED]>
---
arch/x86/lguest/Kconfig | 5 +
arch/x86/lguest/boot.c | 21 +++
drivers/lguest/Makefile | 3 +
drivers/lguest/lguest_device.c | 373 +++++++++++++++++++++++++++++++++++++++
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 44dccfd..c4dffbe 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 959aeeb..495e46a 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 a63f75d..5e8272d 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 0000000..71c6483
--- /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 5ec04a2..61e1e3e 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;
};
/*:*/
-
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
