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OK, this has the big virtio 1.0 implementation, as specified by OASIS.

Browse source 
On top of tht is the major rework of lguest, to use PCI and virtio 1.0, to
 double-check the implementation.
 
 Then comes the inevitable fixes and cleanups from that work.
 
 Thanks,
 Rusty.
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Merge tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull virtio updates from Rusty Russell:
 "OK, this has the big virtio 1.0 implementation, as specified by OASIS.

  On top of tht is the major rework of lguest, to use PCI and virtio
  1.0, to double-check the implementation.

  Then comes the inevitable fixes and cleanups from that work"

* tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (80 commits)
  virtio: don't set VIRTIO_CONFIG_S_DRIVER_OK twice.
  virtio_net: unconditionally define struct virtio_net_hdr_v1.
  tools/lguest: don't use legacy definitions for net device in example launcher.
  virtio: Don't expose legacy net features when VIRTIO_NET_NO_LEGACY defined.
  tools/lguest: use common error macros in the example launcher.
  tools/lguest: give virtqueues names for better error messages
  tools/lguest: more documentation and checking of virtio 1.0 compliance.
  lguest: don't look in console features to find emerg_wr.
  tools/lguest: don't start devices until DRIVER_OK status set.
  tools/lguest: handle indirect partway through chain.
  tools/lguest: insert driver references from the 1.0 spec (4.1 Virtio Over PCI)
  tools/lguest: insert device references from the 1.0 spec (4.1 Virtio Over PCI)
  tools/lguest: rename virtio_pci_cfg_cap field to match spec.
  tools/lguest: fix features_accepted logic in example launcher.
  tools/lguest: handle device reset correctly in example launcher.
  virtual: Documentation: simplify and generalize paravirt_ops.txt
  lguest: remove NOTIFY call and eventfd facility.
  lguest: remove NOTIFY facility from demonstration launcher.
  lguest: use the PCI console device's emerg_wr for early boot messages.
  lguest: always put console in PCI slot #1.
  ...
This commit is contained in:
Linus Torvalds 2015-02-18 09:24:01 -08:00
commit 53861af9a1
43 changed files with 3367 additions and 1605 deletions
Download patch file Download diff file Expand all files Collapse all files

3
drivers/lguest/Makefile
View file

@ -1,6 +1,3 @@
# 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 \

29
drivers/lguest/core.c
View file

@ -208,6 +208,14 @@ void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b,
*/
int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
{
/* If the launcher asked for a register with LHREQ_GETREG */
if (cpu->reg_read) {
if (put_user(*cpu->reg_read, user))
return -EFAULT;
cpu->reg_read = NULL;
return sizeof(*cpu->reg_read);
}
/* We stop running once the Guest is dead. */
while (!cpu->lg->dead) {
unsigned int irq;
@ -217,21 +225,12 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
if (cpu->hcall)
do_hypercalls(cpu);
/*
* It's possible the Guest did a NOTIFY hypercall to the
* Launcher.
*/
if (cpu->pending_notify) {
/*
* Does it just needs to write to a registered
* eventfd (ie. the appropriate virtqueue thread)?
*/
if (!send_notify_to_eventfd(cpu)) {
/* OK, we tell the main Launcher. */
if (put_user(cpu->pending_notify, user))
return -EFAULT;
return sizeof(cpu->pending_notify);
}
/* Do we have to tell the Launcher about a trap? */
if (cpu->pending.trap) {
if (copy_to_user(user, &cpu->pending,
sizeof(cpu->pending)))
return -EFAULT;
return sizeof(cpu->pending);
}
/*

7
drivers/lguest/hypercalls.c
View file

@ -117,9 +117,6 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
/* Similarly, this sets the halted flag for run_guest(). */
cpu->halted = 1;
break;
case LHCALL_NOTIFY:
cpu->pending_notify = args->arg1;
break;
default:
/* It should be an architecture-specific hypercall. */
if (lguest_arch_do_hcall(cpu, args))
@ -189,7 +186,7 @@ static void do_async_hcalls(struct lg_cpu *cpu)
* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first.
*/
if (cpu->pending_notify)
if (cpu->pending.trap)
break;
}
}
@ -280,7 +277,7 @@ void do_hypercalls(struct lg_cpu *cpu)
* NOTIFY to the Launcher, we want to return now. Otherwise we do
* the hypercall.
*/
if (!cpu->pending_notify) {
if (!cpu->pending.trap) {
do_hcall(cpu, cpu->hcall);
/*
* Tricky point: we reset the hcall pointer to mark the

26
drivers/lguest/lg.h
View file

@ -50,7 +50,10 @@ struct lg_cpu {
/* Bitmap of what has changed: see CHANGED_* above. */
int changed;
unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
/* Pending operation. */
struct lguest_pending pending;
unsigned long *reg_read; /* register from LHREQ_GETREG */
/* At end of a page shared mapped over lguest_pages in guest. */
unsigned long regs_page;
@ -78,24 +81,18 @@ struct lg_cpu {
struct lg_cpu_arch arch;
};
struct lg_eventfd {
unsigned long addr;
struct eventfd_ctx *event;
};
struct lg_eventfd_map {
unsigned int num;
struct lg_eventfd map[];
};
/* The private info the thread maintains about the guest. */
struct lguest {
struct lguest_data __user *lguest_data;
struct lg_cpu cpus[NR_CPUS];
unsigned int nr_cpus;
/* Valid guest memory pages must be < this. */
u32 pfn_limit;
/* Device memory is >= pfn_limit and < device_limit. */
u32 device_limit;
/*
* This provides the offset to the base of guest-physical memory in the
* Launcher.
@ -110,8 +107,6 @@ struct lguest {
unsigned int stack_pages;
u32 tsc_khz;
struct lg_eventfd_map *eventfds;
/* Dead? */
const char *dead;
};
@ -197,8 +192,10 @@ void guest_pagetable_flush_user(struct lg_cpu *cpu);
void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir,
unsigned long vaddr, pte_t val);
void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);
bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);
bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode,
unsigned long *iomem);
void pin_page(struct lg_cpu *cpu, unsigned long vaddr);
bool __guest_pa(struct lg_cpu *cpu, unsigned long vaddr, unsigned long *paddr);
unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr);
void page_table_guest_data_init(struct lg_cpu *cpu);
@ -210,6 +207,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu);
int lguest_arch_init_hypercalls(struct lg_cpu *cpu);
int lguest_arch_do_hcall(struct lg_cpu *cpu, struct hcall_args *args);
void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start);
unsigned long *lguest_arch_regptr(struct lg_cpu *cpu, size_t reg_off, bool any);
/* <arch>/switcher.S: */
extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];

540
drivers/lguest/lguest_device.c
View file

@ -1,540 +0,0 @@
/*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 Guest
* 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" or two 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 <linux/export.h>
#include <linux/slab.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;
/*
* 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_cache(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(vd) container_of(vd, struct lguest_device, vdev)
/*D:130
* Device configurations
*
* The configuration information for a device consists of one or more
* virtqueues, a feature bitmap, 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 gets the device's feature bits. */
static u64 lg_get_features(struct virtio_device *vdev)
{
unsigned int i;
u32 features = 0;
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
u8 *in_features = lg_features(desc);
/* We do this the slow but generic way. */
for (i = 0; i < min(desc->feature_len * 8, 32); i++)
if (in_features[i / 8] & (1 << (i % 8)))
features |= (1 << i);
return features;
}
/*
* To notify on reset or feature finalization, we (ab)use the NOTIFY
* hypercall, with the descriptor address of the device.
*/
static void status_notify(struct virtio_device *vdev)
{
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
hcall(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset, 0, 0, 0);
}
/*
* The virtio core takes the features the Host offers, and copies the ones
* supported by the driver into the vdev->features array. Once that's all
* sorted out, this routine is called so we can tell the Host which features we
* understand and accept.
*/
static int lg_finalize_features(struct virtio_device *vdev)
{
unsigned int i, bits;
struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
/* Second half of bitmap is features we accept. */
u8 *out_features = lg_features(desc) + desc->feature_len;
/* Give virtio_ring a chance to accept features. */
vring_transport_features(vdev);
/* Make sure we don't have any features > 32 bits! */
BUG_ON((u32)vdev->features != vdev->features);
/*
* Since lguest is currently x86-only, we're little-endian. That
* means we could just memcpy. But it's not time critical, and in
* case someone copies this code, we do it the slow, obvious way.
*/
memset(out_features, 0, desc->feature_len);
bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
for (i = 0; i < bits; i++) {
if (__virtio_test_bit(vdev, i))
out_features[i / 8] |= (1 << (i % 8));
}
/* Tell Host we've finished with this device's feature negotiation */
status_notify(vdev);
return 0;
}
/* 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;
/* Tell Host immediately if we failed. */
if (status & VIRTIO_CONFIG_S_FAILED)
status_notify(vdev);
}
static void lg_reset(struct virtio_device *vdev)
{
/* 0 status means "reset" */
to_lgdev(vdev)->desc->status = 0;
status_notify(vdev);
}
/*
* 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 physical address of the virtqueue so the Host
* knows which virtqueue we're talking about.
*/
static bool 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, 0);
return true;
}
/* An extern declaration inside a C file is bad form. Don't do it. */
extern int lguest_setup_irq(unsigned int irq);
/*
* This routine finds the Nth 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.
*/
static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
unsigned index,
void (*callback)(struct virtqueue *vq),
const char *name)
{
struct lguest_device *ldev = to_lgdev(vdev);
struct lguest_vq_info *lvq;
struct virtqueue *vq;
int err;
if (!name)
return NULL;
/* 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,
LGUEST_VRING_ALIGN),
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. Note that we set weak_barriers
* to 'true': the host just a(nother) SMP CPU, so we only need inter-cpu
* barriers.
*/
vq = vring_new_virtqueue(index, lvq->config.num, LGUEST_VRING_ALIGN, vdev,
true, lvq->pages, lg_notify, callback, name);
if (!vq) {
err = -ENOMEM;
goto unmap;
}
/* Make sure the interrupt is allocated. */
err = lguest_setup_irq(lvq->config.irq);
if (err)
goto destroy_vring;
/*
* 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,
dev_name(&vdev->dev), vq);
if (err)
goto free_desc;
/*
* Last of all we hook up our 'struct lguest_vq_info" to the
* virtqueue's priv pointer.
*/
vq->priv = lvq;
return vq;
free_desc:
irq_free_desc(lvq->config.irq);
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);
}
static void lg_del_vqs(struct virtio_device *vdev)
{
struct virtqueue *vq, *n;
list_for_each_entry_safe(vq, n, &vdev->vqs, list)
lg_del_vq(vq);
}
static int lg_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[])
{
struct lguest_device *ldev = to_lgdev(vdev);
int i;
/* We must have this many virtqueues. */
if (nvqs > ldev->desc->num_vq)
return -ENOENT;
for (i = 0; i < nvqs; ++i) {
vqs[i] = lg_find_vq(vdev, i, callbacks[i], names[i]);
if (IS_ERR(vqs[i]))
goto error;
}
return 0;
error:
lg_del_vqs(vdev);
return PTR_ERR(vqs[i]);
}
static const char *lg_bus_name(struct virtio_device *vdev)
{
return "";
}
/* The ops structure which hooks everything together. */
static const struct virtio_config_ops lguest_config_ops = {
.get_features = lg_get_features,
.finalize_features = lg_finalize_features,
.get = lg_get,
.set = lg_set,
.get_status = lg_get_status,
.set_status = lg_set_status,
.reset = lg_reset,
.find_vqs = lg_find_vqs,
.del_vqs = lg_del_vqs,
.bus_name = lg_bus_name,
};
/*
* 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;
/*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, and the offset into the device
* descriptor page so we can uniquely identify it if things go badly wrong.
*/
static void add_lguest_device(struct lguest_device_desc *d,
unsigned int offset)
{
struct lguest_device *ldev;
/* Start with zeroed memory; Linux's device layer counts on it. */
ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
if (!ldev) {
printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n",
offset, d->type);
return;
}
/* This devices' parent is the lguest/ dir. */
ldev->vdev.dev.parent = lguest_root;
/*
* 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 dev %u type %u\n",
offset, d->type);
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, i);
}
}
/*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;
lguest_root = root_device_register("lguest");
if (IS_ERR(lguest_root))
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?".
*/

237
drivers/lguest/lguest_user.c
View file

@ -2,175 +2,62 @@
* launcher controls and communicates with the Guest. For example,
* the first write will tell us the Guest's memory layout and entry
* point. A read will run the Guest until something happens, such as
* a signal or the Guest doing a NOTIFY out to the Launcher. There is
* also a way for the Launcher to attach eventfds to particular NOTIFY
* values instead of returning from the read() call.
* a signal or the Guest accessing a device.
:*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/eventfd.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/export.h>
#include "lg.h"
/*L:056
* Before we move on, let's jump ahead and look at what the kernel does when
* it needs to look up the eventfds. That will complete our picture of how we
* use RCU.
*
* The notification value is in cpu->pending_notify: we return true if it went
* to an eventfd.
*/
bool send_notify_to_eventfd(struct lg_cpu *cpu)
{
unsigned int i;
struct lg_eventfd_map *map;
/*
* This "rcu_read_lock()" helps track when someone is still looking at
* the (RCU-using) eventfds array. It's not actually a lock at all;
* indeed it's a noop in many configurations. (You didn't expect me to
* explain all the RCU secrets here, did you?)
*/
rcu_read_lock();
/*
* rcu_dereference is the counter-side of rcu_assign_pointer(); it
* makes sure we don't access the memory pointed to by
* cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy,
* but Alpha allows this! Paul McKenney points out that a really
* aggressive compiler could have the same effect:
* http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html
*
* So play safe, use rcu_dereference to get the rcu-protected pointer:
*/
map = rcu_dereference(cpu->lg->eventfds);
/*
* Simple array search: even if they add an eventfd while we do this,
* we'll continue to use the old array and just won't see the new one.
*/
for (i = 0; i < map->num; i++) {
if (map->map[i].addr == cpu->pending_notify) {
eventfd_signal(map->map[i].event, 1);
cpu->pending_notify = 0;
break;
}
}
/* We're done with the rcu-protected variable cpu->lg->eventfds. */
rcu_read_unlock();
/* If we cleared the notification, it's because we found a match. */
return cpu->pending_notify == 0;
}
/*L:055
* One of the more tricksy tricks in the Linux Kernel is a technique called
* Read Copy Update. Since one point of lguest is to teach lguest journeyers
* about kernel coding, I use it here. (In case you're curious, other purposes
* include learning about virtualization and instilling a deep appreciation for
* simplicity and puppies).
*
* We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we
* add new eventfds without ever blocking readers from accessing the array.
* The current Launcher only does this during boot, so that never happens. But
* Read Copy Update is cool, and adding a lock risks damaging even more puppies
* than this code does.
*
* We allocate a brand new one-larger array, copy the old one and add our new
* element. Then we make the lg eventfd pointer point to the new array.
* That's the easy part: now we need to free the old one, but we need to make
* sure no slow CPU somewhere is still looking at it. That's what
* synchronize_rcu does for us: waits until every CPU has indicated that it has
* moved on to know it's no longer using the old one.
*
* If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update.
*/
static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
{
struct lg_eventfd_map *new, *old = lg->eventfds;
/*
* We don't allow notifications on value 0 anyway (pending_notify of
* 0 means "nothing pending").
*/
if (!addr)
return -EINVAL;
/*
* Replace the old array with the new one, carefully: others can
* be accessing it at the same time.
*/
new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
GFP_KERNEL);
if (!new)
return -ENOMEM;
/* First make identical copy. */
memcpy(new->map, old->map, sizeof(old->map[0]) * old->num);
new->num = old->num;
/* Now append new entry. */
new->map[new->num].addr = addr;
new->map[new->num].event = eventfd_ctx_fdget(fd);
if (IS_ERR(new->map[new->num].event)) {
int err = PTR_ERR(new->map[new->num].event);
kfree(new);
return err;
}
new->num++;
/*
* Now put new one in place: rcu_assign_pointer() is a fancy way of
* doing "lg->eventfds = new", but it uses memory barriers to make
* absolutely sure that the contents of "new" written above is nailed
* down before we actually do the assignment.
*
* We have to think about these kinds of things when we're operating on
* live data without locks.
*/
rcu_assign_pointer(lg->eventfds, new);
/*
* We're not in a big hurry. Wait until no one's looking at old
* version, then free it.
*/
synchronize_rcu();
kfree(old);
return 0;
}
/*L:052
* Receiving notifications from the Guest is usually done by attaching a
* particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will
* become readable when the Guest does an LHCALL_NOTIFY with that value.
*
* This is really convenient for processing each virtqueue in a separate
* thread.
*/
static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
The Launcher can get the registers, and also set some of them.
*/
static int getreg_setup(struct lg_cpu *cpu, const unsigned long __user *input)
{
unsigned long addr, fd;
int err;
unsigned long which;
if (get_user(addr, input) != 0)
/* We re-use the ptrace structure to specify which register to read. */
if (get_user(which, input) != 0)
return -EFAULT;
/*
* We set up the cpu register pointer, and their next read will
* actually get the value (instead of running the guest).
*
* The last argument 'true' says we can access any register.
*/
cpu->reg_read = lguest_arch_regptr(cpu, which, true);
if (!cpu->reg_read)
return -ENOENT;
/* And because this is a write() call, we return the length used. */
return sizeof(unsigned long) * 2;
}
static int setreg(struct lg_cpu *cpu, const unsigned long __user *input)
{
unsigned long which, value, *reg;
/* We re-use the ptrace structure to specify which register to read. */
if (get_user(which, input) != 0)
return -EFAULT;
input++;
if (get_user(fd, input) != 0)
if (get_user(value, input) != 0)
return -EFAULT;
/*
* Just make sure two callers don't add eventfds at once. We really
* only need to lock against callers adding to the same Guest, so using
* the Big Lguest Lock is overkill. But this is setup, not a fast path.
*/
mutex_lock(&lguest_lock);
err = add_eventfd(lg, addr, fd);
mutex_unlock(&lguest_lock);
/* The last argument 'false' means we can't access all registers. */
reg = lguest_arch_regptr(cpu, which, false);
if (!reg)
return -ENOENT;
return err;
*reg = value;
/* And because this is a write() call, we return the length used. */
return sizeof(unsigned long) * 3;
}
/*L:050
@ -194,6 +81,23 @@ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
return 0;
}
/*L:053
* Deliver a trap: this is used by the Launcher if it can't emulate
* an instruction.
*/
static int trap(struct lg_cpu *cpu, const unsigned long __user *input)
{
unsigned long trapnum;
if (get_user(trapnum, input) != 0)
return -EFAULT;
if (!deliver_trap(cpu, trapnum))
return -EINVAL;
return 0;
}
/*L:040
* Once our Guest is initialized, the Launcher makes it run by reading
* from /dev/lguest.
@ -237,8 +141,8 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
* If we returned from read() last time because the Guest sent I/O,
* clear the flag.
*/
if (cpu->pending_notify)
cpu->pending_notify = 0;
if (cpu->pending.trap)
cpu->pending.trap = 0;
/* Run the Guest until something interesting happens. */
return run_guest(cpu, (unsigned long __user *)user);
@ -319,7 +223,7 @@ static int initialize(struct file *file, const unsigned long __user *input)
/* "struct lguest" contains all we (the Host) know about a Guest. */
struct lguest *lg;
int err;
unsigned long args[3];
unsigned long args[4];
/*
* We grab the Big Lguest lock, which protects against multiple
@ -343,21 +247,15 @@ static int initialize(struct file *file, const unsigned long __user *input)
goto unlock;
}
lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL);
if (!lg->eventfds) {
err = -ENOMEM;
goto free_lg;
}
lg->eventfds->num = 0;
/* Populate the easy fields of our "struct lguest" */
lg->mem_base = (void __user *)args[0];
lg->pfn_limit = args[1];
lg->device_limit = args[3];
/* This is the first cpu (cpu 0) and it will start booting at args[2] */
err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
if (err)
goto free_eventfds;
goto free_lg;
/*
* Initialize the Guest's shadow page tables. This allocates
@ -378,8 +276,6 @@ static int initialize(struct file *file, const unsigned long __user *input)
free_regs:
/* FIXME: This should be in free_vcpu */
free_page(lg->cpus[0].regs_page);
free_eventfds:
kfree(lg->eventfds);
free_lg:
kfree(lg);
unlock:
@ -432,8 +328,12 @@ static ssize_t write(struct file *file, const char __user *in,
return initialize(file, input);
case LHREQ_IRQ:
return user_send_irq(cpu, input);
case LHREQ_EVENTFD:
return attach_eventfd(lg, input);
case LHREQ_GETREG:
return getreg_setup(cpu, input);
case LHREQ_SETREG:
return setreg(cpu, input);
case LHREQ_TRAP:
return trap(cpu, input);
default:
return -EINVAL;
}
@ -478,11 +378,6 @@ static int close(struct inode *inode, struct file *file)
mmput(lg->cpus[i].mm);
}
/* Release any eventfds they registered. */
for (i = 0; i < lg->eventfds->num; i++)
eventfd_ctx_put(lg->eventfds->map[i].event);
kfree(lg->eventfds);
/*
* If lg->dead doesn't contain an error code it will be NULL or a
* kmalloc()ed string, either of which is ok to hand to kfree().

75
drivers/lguest/page_tables.c
View file

@ -250,6 +250,16 @@ static void release_pte(pte_t pte)
}
/*:*/
static bool gpte_in_iomem(struct lg_cpu *cpu, pte_t gpte)
{
/* We don't handle large pages. */
if (pte_flags(gpte) & _PAGE_PSE)
return false;
return (pte_pfn(gpte) >= cpu->lg->pfn_limit
&& pte_pfn(gpte) < cpu->lg->device_limit);
}
static bool check_gpte(struct lg_cpu *cpu, pte_t gpte)
{
if ((pte_flags(gpte) & _PAGE_PSE) ||
@ -374,8 +384,14 @@ static pte_t *find_spte(struct lg_cpu *cpu, unsigned long vaddr, bool allocate,
*
* If we fixed up the fault (ie. we mapped the address), this routine returns
* true. Otherwise, it was a real fault and we need to tell the Guest.
*
* There's a corner case: they're trying to access memory between
* pfn_limit and device_limit, which is I/O memory. In this case, we
* return false and set @iomem to the physical address, so the the
* Launcher can handle the instruction manually.
*/
bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode,
unsigned long *iomem)
{
unsigned long gpte_ptr;
pte_t gpte;
@ -383,6 +399,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
pmd_t gpmd;
pgd_t gpgd;
*iomem = 0;
/* We never demand page the Switcher, so trying is a mistake. */
if (vaddr >= switcher_addr)
return false;
@ -459,6 +477,12 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))
return false;
/* If they're accessing io memory, we expect a fault. */
if (gpte_in_iomem(cpu, gpte)) {
*iomem = (pte_pfn(gpte) << PAGE_SHIFT) | (vaddr & ~PAGE_MASK);
return false;
}
/*
* Check that the Guest PTE flags are OK, and the page number is below
* the pfn_limit (ie. not mapping the Launcher binary).
@ -553,7 +577,9 @@ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
*/
void pin_page(struct lg_cpu *cpu, unsigned long vaddr)
{
if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))
unsigned long iomem;
if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2, &iomem))
kill_guest(cpu, "bad stack page %#lx", vaddr);
}
/*:*/
@ -647,7 +673,7 @@ void guest_pagetable_flush_user(struct lg_cpu *cpu)
/*:*/
/* We walk down the guest page tables to get a guest-physical address */
unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
bool __guest_pa(struct lg_cpu *cpu, unsigned long vaddr, unsigned long *paddr)
{
pgd_t gpgd;
pte_t gpte;
@ -656,31 +682,47 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
#endif
/* Still not set up? Just map 1:1. */
if (unlikely(cpu->linear_pages))
return vaddr;
if (unlikely(cpu->linear_pages)) {
*paddr = vaddr;
return true;
}
/* First step: get the top-level Guest page table entry. */
gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
/* Toplevel not present? We can't map it in. */
if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) {
kill_guest(cpu, "Bad address %#lx", vaddr);
return -1UL;
}
if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
goto fail;
#ifdef CONFIG_X86_PAE
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) {
kill_guest(cpu, "Bad address %#lx", vaddr);
return -1UL;
}
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
goto fail;
gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t);
#else
gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);
#endif
if (!(pte_flags(gpte) & _PAGE_PRESENT))
kill_guest(cpu, "Bad address %#lx", vaddr);
goto fail;
return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
*paddr = pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
return true;
fail:
*paddr = -1UL;
return false;
}
/*
* This is the version we normally use: kills the Guest if it uses a
* bad address
*/
unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
{
unsigned long paddr;
if (!__guest_pa(cpu, vaddr, &paddr))
kill_guest(cpu, "Bad address %#lx", vaddr);
return paddr;
}
/*
@ -912,7 +954,8 @@ static void __guest_set_pte(struct lg_cpu *cpu, int idx,
* now. This shaves 10% off a copy-on-write
* micro-benchmark.
*/
if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
if ((pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED))
&& !gpte_in_iomem(cpu, gpte)) {
if (!check_gpte(cpu, gpte))
return;
set_pte(spte,

194
drivers/lguest/x86/core.c
View file

@ -182,6 +182,52 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
}
/*:*/
unsigned long *lguest_arch_regptr(struct lg_cpu *cpu, size_t reg_off, bool any)
{
switch (reg_off) {
case offsetof(struct pt_regs, bx):
return &cpu->regs->ebx;
case offsetof(struct pt_regs, cx):
return &cpu->regs->ecx;
case offsetof(struct pt_regs, dx):
return &cpu->regs->edx;
case offsetof(struct pt_regs, si):
return &cpu->regs->esi;
case offsetof(struct pt_regs, di):
return &cpu->regs->edi;
case offsetof(struct pt_regs, bp):
return &cpu->regs->ebp;
case offsetof(struct pt_regs, ax):
return &cpu->regs->eax;
case offsetof(struct pt_regs, ip):
return &cpu->regs->eip;
case offsetof(struct pt_regs, sp):
return &cpu->regs->esp;
}
/* Launcher can read these, but we don't allow any setting. */
if (any) {
switch (reg_off) {
case offsetof(struct pt_regs, ds):
return &cpu->regs->ds;
case offsetof(struct pt_regs, es):
return &cpu->regs->es;
case offsetof(struct pt_regs, fs):
return &cpu->regs->fs;
case offsetof(struct pt_regs, gs):
return &cpu->regs->gs;
case offsetof(struct pt_regs, cs):
return &cpu->regs->cs;
case offsetof(struct pt_regs, flags):
return &cpu->regs->eflags;
case offsetof(struct pt_regs, ss):
return &cpu->regs->ss;
}
}
return NULL;
}
/*M:002
* There are hooks in the scheduler which we can register to tell when we
* get kicked off the CPU (preempt_notifier_register()). This would allow us
@ -269,110 +315,73 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
* usually attached to a PC.
*
* When the Guest uses one of these instructions, we get a trap (General
* Protection Fault) and come here. We see if it's one of those troublesome
* instructions and skip over it. We return true if we did.
* Protection Fault) and come here. We queue this to be sent out to the
* Launcher to handle.
*/
static int emulate_insn(struct lg_cpu *cpu)
/*
* The eip contains the *virtual* address of the Guest's instruction:
* we copy the instruction here so the Launcher doesn't have to walk
* the page tables to decode it. We handle the case (eg. in a kernel
* module) where the instruction is over two pages, and the pages are
* virtually but not physically contiguous.
*
* The longest possible x86 instruction is 15 bytes, but we don't handle
* anything that strange.
*/
static void copy_from_guest(struct lg_cpu *cpu,
void *dst, unsigned long vaddr, size_t len)
{
u8 insn;
unsigned int insnlen = 0, in = 0, small_operand = 0;
/*
* The eip contains the *virtual* address of the Guest's instruction:
* walk the Guest's page tables to find the "physical" address.
*/
unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
size_t to_page_end = PAGE_SIZE - (vaddr % PAGE_SIZE);
unsigned long paddr;
/*
* This must be the Guest kernel trying to do something, not userspace!
* The bottom two bits of the CS segment register are the privilege
* level.
*/
if ((cpu->regs->cs & 3) != GUEST_PL)
return 0;
BUG_ON(len > PAGE_SIZE);
/* Decoding x86 instructions is icky. */
insn = lgread(cpu, physaddr, u8);
/*
* Around 2.6.33, the kernel started using an emulation for the
* cmpxchg8b instruction in early boot on many configurations. This
* code isn't paravirtualized, and it tries to disable interrupts.
* Ignore it, which will Mostly Work.
*/
if (insn == 0xfa) {
/* "cli", or Clear Interrupt Enable instruction. Skip it. */
cpu->regs->eip++;
return 1;
/* If it goes over a page, copy in two parts. */
if (len > to_page_end) {
/* But make sure the next page is mapped! */
if (__guest_pa(cpu, vaddr + to_page_end, &paddr))
copy_from_guest(cpu, dst + to_page_end,
vaddr + to_page_end,
len - to_page_end);
else
/* Otherwise fill with zeroes. */
memset(dst + to_page_end, 0, len - to_page_end);
len = to_page_end;
}
/*
* 0x66 is an "operand prefix". It means a 16, not 32 bit in/out.
*/
if (insn == 0x66) {
small_operand = 1;
/* The instruction is 1 byte so far, read the next byte. */
insnlen = 1;
insn = lgread(cpu, physaddr + insnlen, u8);
}
/* This will kill the guest if it isn't mapped, but that
* shouldn't happen. */
__lgread(cpu, dst, guest_pa(cpu, vaddr), len);
}
/*
* We can ignore the lower bit for the moment and decode the 4 opcodes
* we need to emulate.
*/
switch (insn & 0xFE) {
case 0xE4: /* in <next byte>,%al */
insnlen += 2;
in = 1;
break;
case 0xEC: /* in (%dx),%al */
insnlen += 1;
in = 1;
break;
case 0xE6: /* out %al,<next byte> */
insnlen += 2;
break;
case 0xEE: /* out %al,(%dx) */
insnlen += 1;
break;
default:
/* OK, we don't know what this is, can't emulate. */
return 0;
}
/*
* If it was an "IN" instruction, they expect the result to be read
* into %eax, so we change %eax. We always return all-ones, which
* traditionally means "there's nothing there".
*/
if (in) {
/* Lower bit tells means it's a 32/16 bit access */
if (insn & 0x1) {
if (small_operand)
cpu->regs->eax |= 0xFFFF;
else
cpu->regs->eax = 0xFFFFFFFF;
} else
cpu->regs->eax |= 0xFF;
}
/* Finally, we've "done" the instruction, so move past it. */
cpu->regs->eip += insnlen;
/* Success! */
return 1;
static void setup_emulate_insn(struct lg_cpu *cpu)
{
cpu->pending.trap = 13;
copy_from_guest(cpu, cpu->pending.insn, cpu->regs->eip,
sizeof(cpu->pending.insn));
}
static void setup_iomem_insn(struct lg_cpu *cpu, unsigned long iomem_addr)
{
cpu->pending.trap = 14;
cpu->pending.addr = iomem_addr;
copy_from_guest(cpu, cpu->pending.insn, cpu->regs->eip,
sizeof(cpu->pending.insn));
}
/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
void lguest_arch_handle_trap(struct lg_cpu *cpu)
{
unsigned long iomem_addr;
switch (cpu->regs->trapnum) {
case 13: /* We've intercepted a General Protection Fault. */
/*
* Check if this was one of those annoying IN or OUT
* instructions which we need to emulate. If so, we just go
* back into the Guest after we've done it.
*/
/* Hand to Launcher to emulate those pesky IN and OUT insns */
if (cpu->regs->errcode == 0) {
if (emulate_insn(cpu))
return;
setup_emulate_insn(cpu);
return;
}
break;
case 14: /* We've intercepted a Page Fault. */
@ -387,9 +396,16 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
* whether kernel or userspace code.
*/
if (demand_page(cpu, cpu->arch.last_pagefault,
cpu->regs->errcode))
cpu->regs->errcode, &iomem_addr))
return;
/* Was this an access to memory mapped IO? */
if (iomem_addr) {
/* Tell Launcher, let it handle it. */
setup_iomem_insn(cpu, iomem_addr);
return;
}
/*
* OK, it's really not there (or not OK): the Guest needs to
* know. We write out the cr2 value so it knows where the