/*
* KVM paravirt_ops implementation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
* Copyright IBM Corporation, 2007
* Authors: Anthony Liguori <aliguori@us.ibm.com>
*/
#include <linux/context_tracking.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kvm_para.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/hardirq.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kprobes.h>
#include <linux/debugfs.h>
#include <linux/nmi.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
#include <asm/desc.h>
#include <asm/tlbflush.h>
#include <asm/idle.h>
#include <asm/apic.h>
#include <asm/apicdef.h>
#include <asm/hypervisor.h>
#include <asm/kvm_guest.h>
static int kvmapf = 1;
static int parse_no_kvmapf(char *arg)
{
kvmapf = 0;
return 0;
}
early_param("no-kvmapf", parse_no_kvmapf);
static int steal_acc = 1;
static int parse_no_stealacc(char *arg)
{
steal_acc = 0;
return 0;
}
early_param("no-steal-acc", parse_no_stealacc);
static int kvmclock_vsyscall = 1;
static int parse_no_kvmclock_vsyscall(char *arg)
{
kvmclock_vsyscall = 0;
return 0;
}
early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
static int has_steal_clock = 0;
/*
* No need for any "IO delay" on KVM
*/
static void kvm_io_delay(void)
{
}
#define KVM_TASK_SLEEP_HASHBITS 8
#define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
struct kvm_task_sleep_node {
struct hlist_node link;
wait_queue_head_t wq;
u32 token;
int cpu;
bool halted;
};
static struct kvm_task_sleep_head {
spinlock_t lock;
struct hlist_head list;
} async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
u32 token)
{
struct hlist_node *p;
hlist_for_each(p, &b->list) {
struct kvm_task_sleep_node *n =
hlist_entry(p, typeof(*n), link);
if (n->token == token)
return n;
}
return NULL;
}
void kvm_async_pf_task_wait(u32 token)
{
u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
struct kvm_task_sleep_node n, *e;
DEFINE_WAIT(wait);
rcu_irq_enter();
spin_lock(&b->lock);
e = _find_apf_task(b, token);
if (e) {
/* dummy entry exist -> wake up was delivered ahead of PF */
hlist_del(&e->link);
kfree(e);
spin_unlock(&b->lock);
rcu_irq_exit();
return;
}
n.token = token;
n.cpu = smp_processor_id();
n.halted = is_idle_task(current) || preempt_count() > 1;
init_waitqueue_head(&n.wq);
hlist_add_head(&n.link, &b->list);
spin_unlock(&b->lock);
for (;;) {
if (!n.halted)
prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
if (hlist_unhashed(&n.link))
break;
if (!n.halted) {
local_irq_enable();
schedule();
local_irq_disable();
} else {
/*
* We cannot reschedule. So halt.
*/
rcu_irq_exit();
native_safe_halt();
rcu_irq_enter();
local_irq_disable();
}
}
if (!n.halted)
finish_wait(&n.wq, &wait);
rcu_irq_exit();
return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
static void apf_task_wake_one(struct kvm_task_sleep_node *n)
{
hlist_del_init(&n->link);
if (n->halted)
smp_send_reschedule(n->cpu);
else if (waitqueue_active(&n->wq))
wake_up(&n->wq);
}
static void apf_task_wake_all(void)
{
int i;
for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
struct hlist_node *p, *next;
struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
spin_lock(&b->lock);
hlist_for_each_safe(p, next, &b->list) {
struct kvm_task_sleep_node *n =
hlist_entry(p, typeof(*n), link);
if (n->cpu == smp_processor_id())
apf_task_wake_one(n);
}
spin_unlock(&b->lock);
}
}
void kvm_async_pf_task_wake(u32 token)
{
u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
struct kvm_task_sleep_node *n;
if (token == ~0) {
apf_task_wake_all();
return;
}
again:
spin_lock(&b->lock);
n = _find_apf_task(b, token);
if (!n) {
/*
* async PF was not yet handled.
* Add dummy entry for the token.
*/
n = kzalloc(sizeof(*n), GFP_ATOMIC);
if (!n) {
/*
* Allocation failed! Busy wait while other cpu
* handles async PF.
*/
spin_unlock(&b->lock);
cpu_relax();
goto again;
}
n->token = token;
n->cpu = smp_processor_id();
init_waitqueue_head(&n->wq);
hlist_add_head(&n->link, &b->list);
} else
apf_task_wake_one(n);
spin_unlock(&b->lock);
return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
u32 kvm_read_and_reset_pf_reason(void)
{
u32 reason = 0;
if (__this_cpu_read(apf_reason.enabled)) {
reason = __this_cpu_read(apf_reason.reason);
__this_cpu_write(apf_reason.reason, 0);
}
return reason;
}
EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
dotraplinkage void
do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
{
enum ctx_state prev_state;
switch (kvm_read_and_reset_pf_reason()) {
default:
trace_do_page_fault(regs, error_code);
break;
case KVM_PV_REASON_PAGE_NOT_PRESENT:
/* page is swapped out by the host. */
prev_state = exception_enter();
exit_idle();
kvm_async_pf_task_wait((u32)read_cr2());
exception_exit(prev_state);
break;
case KVM_PV_REASON_PAGE_READY:
rcu_irq_enter();
exit_idle();
kvm_async_pf_task_wake((u32)read_cr2());
rcu_irq_exit();
break;
}
}
NOKPROBE_SYMBOL(do_async_page_fault);
static void __init paravirt_ops_setup(void)
{
pv_info.name = "KVM";
/*
* KVM isn't paravirt in the sense of paravirt_enabled. A KVM
* guest kernel works like a bare metal kernel with additional
* features, and paravirt_enabled is about features that are
* missing.
*/
pv_info.paravirt_enabled = 0;
if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
pv_cpu_ops.io_delay = kvm_io_delay;
#ifdef CONFIG_X86_IO_APIC
no_timer_check = 1;
#endif
}
static void kvm_register_steal_time(void)
{
int cpu = smp_processor_id();
struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
if (!has_steal_clock)
return;
memset(st, 0, sizeof(*st));
wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
pr_info("kvm-stealtime: cpu %d, msr %llx\n",
cpu, (unsigned long long) slow_virt_to_phys(st));
}
static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
{
/**
* This relies on __test_and_clear_bit to modify the memory
* in a way that is atomic with respect to the local CPU.
* The hypervisor only accesses this memory from the local CPU so
* there's no need for lock or memory barriers.
* An optimization barrier is implied in apic write.
*/
if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
return;
apic_write(APIC_EOI, APIC_EOI_ACK);
}
void kvm_guest_cpu_init(void)
{
if (!kvm_para_available())
return;
if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
#ifdef CONFIG_PREEMPT
pa |= KVM_ASYNC_PF_SEND_ALWAYS;
#endif
wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
__this_cpu_write(apf_reason.enabled, 1);
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
smp_processor_id());
}
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
unsigned long pa;
/* Size alignment is implied but just to make it explicit. */
BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
__this_cpu_write(kvm_apic_eoi, 0);
pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
| KVM_MSR_ENABLED;
wrmsrl(MSR_KVM_PV_EOI_EN, pa);
}
if (has_steal_clock)
kvm_register_steal_time();
}
static void kvm_pv_disable_apf(void)
{
if (!__this_cpu_read(apf_reason.enabled))
return;
wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
__this_cpu_write(apf_reason.enabled, 0);
printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
smp_processor_id());
}
static void kvm_pv_guest_cpu_reboot(void *unused)
{
/*
* We disable PV EOI before we load a new kernel by kexec,
* since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
* New kernel can re-enable when it boots.
*/
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
wrmsrl(MSR_KVM_PV_EOI_EN, 0);
kvm_pv_disable_apf();
kvm_disable_steal_time();
}
static int kvm_pv_reboot_notify(struct notifier_block *nb,
unsigned long code, void *unused)
{
if (code == SYS_RESTART)
on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
return NOTIFY_DONE;
}
static struct notifier_block kvm_pv_reboot_nb = {
.notifier_call = kvm_pv_reboot_notify,
};
static u64 kvm_steal_clock(int cpu)
{
u64 steal;
struct kvm_steal_time *src;
int version;
src = &per_cpu(steal_time, cpu);
do {
version = src->version;
rmb();
steal = src->steal;
rmb();
} while ((version & 1) || (version != src->version));
return steal;
}
void kvm_disable_steal_time(void)
{
if (!has_steal_clock)
return;
wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}
#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_boot_cpu(void)
{
kvm_guest_cpu_init();
native_smp_prepare_boot_cpu();
kvm_spinlock_init();
}
static void kvm_guest_cpu_online(void *dummy)
{
kvm_guest_cpu_init();
}
static void kvm_guest_cpu_offline(void *dummy)
{
kvm_disable_steal_time();
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
wrmsrl(MSR_KVM_PV_EOI_EN, 0);
kvm_pv_disable_apf();
apf_task_wake_all();
}
static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
void *hcpu)
{
int cpu = (unsigned long)hcpu;
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
case CPU_ONLINE_FROZEN:
smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block kvm_cpu_notifier = {
.notifier_call = kvm_cpu_notify,
};
#endif
static void __init kvm_apf_trap_init(void)
{
set_intr_gate(14, async_page_fault);
}
void __init kvm_guest_init(void)
{
int i;
if (!kvm_para_available())
return;
paravirt_ops_setup();
register_reboot_notifier(&kvm_pv_reboot_nb);
for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
spin_lock_init(&async_pf_sleepers[i].lock);
if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
x86_init.irqs.trap_init = kvm_apf_trap_init;
if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
has_steal_clock = 1;
pv_time_ops.steal_clock = kvm_steal_clock;
}
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
apic_set_eoi_write(kvm_guest_apic_eoi_write);
if (kvmclock_vsyscall)
kvm_setup_vsyscall_timeinfo();
#ifdef CONFIG_SMP
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
register_cpu_notifier(&kvm_cpu_notifier);
#else
kvm_guest_cpu_init();
#endif
/*
* Hard lockup detection is enabled by default. Disable it, as guests
* can get false positives too easily, for example if the host is
* overcommitted.
*/
hardlockup_detector_disable();
}
static noinline uint32_t __kvm_cpuid_base(void)
{
if (boot_cpu_data.cpuid_level < 0)
return 0; /* So we don't blow up on old processors */
if (cpu_has_hypervisor)
return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
return 0;
}
static inline uint32_t kvm_cpuid_base(void)
{
static int kvm_cpuid_base = -1;
if (kvm_cpuid_base == -1)
kvm_cpuid_base = __kvm_cpuid_base();
return kvm_cpuid_base;
}
bool kvm_para_available(void)
{
return kvm_cpuid_base() != 0;
}
EXPORT_SYMBOL_GPL(kvm_para_available);
unsigned int kvm_arch_para_features(void)
{
return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
}
static uint32_t __init kvm_detect(void)
{
return kvm_cpuid_base();
}
const struct hypervisor_x86 x86_hyper_kvm __refconst = {
.name = "KVM",
.detect = kvm_detect,
.x2apic_available = kvm_para_available,
};
EXPORT_SYMBOL_GPL(x86_hyper_kvm);
static __init int activate_jump_labels(void)
{
if (has_steal_clock) {
static_key_slow_inc(¶virt_steal_enabled);
if (steal_acc)
static_key_slow_inc(¶virt_steal_rq_enabled);
}
return 0;
}
arch_initcall(activate_jump_labels);
#ifdef CONFIG_PARAVIRT_SPINLOCKS
/* Kick a cpu by its apicid. Used to wake up a halted vcpu */
static void kvm_kick_cpu(int cpu)
{
int apicid;
unsigned long flags = 0;
apicid = per_cpu(x86_cpu_to_apicid, cpu);
kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
}
enum kvm_contention_stat {
TAKEN_SLOW,
TAKEN_SLOW_PICKUP,
RELEASED_SLOW,
RELEASED_SLOW_KICKED,
NR_CONTENTION_STATS
};
#ifdef CONFIG_KVM_DEBUG_FS
#define HISTO_BUCKETS 30
static struct kvm_spinlock_stats
{
u32 contention_stats[NR_CONTENTION_STATS];
u32 histo_spin_blocked[HISTO_BUCKETS+1];
u64 time_blocked;
} spinlock_stats;
static u8 zero_stats;
static inline void check_zero(void)
{
u8 ret;
u8 old;
old = READ_ONCE(zero_stats);
if (unlikely(old)) {
ret = cmpxchg(&zero_stats, old, 0);
/* This ensures only one fellow resets the stat */
if (ret == old)
memset(&spinlock_stats, 0, sizeof(spinlock_stats));
}
}
static inline void add_stats(enum kvm_contention_stat var, u32 val)
{
check_zero();
spinlock_stats.contention_stats[var] += val;
}
static inline u64 spin_time_start(void)
{
return sched_clock();
}
static void __spin_time_accum(u64 delta, u32 *array)
{
unsigned index;
index = ilog2(delta);
check_zero();
if (index < HISTO_BUCKETS)
array[index]++;
else
array[HISTO_BUCKETS]++;
}
static inline void spin_time_accum_blocked(u64 start)
{
u32 delta;
delta = sched_clock() - start;
__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
spinlock_stats.time_blocked += delta;
}
static struct dentry *d_spin_debug;
static struct dentry *d_kvm_debug;
struct dentry *kvm_init_debugfs(void)
{
d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
if (!d_kvm_debug)
printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
return d_kvm_debug;
}
static int __init kvm_spinlock_debugfs(void)
{
struct dentry *d_kvm;
d_kvm = kvm_init_debugfs();
if (d_kvm == NULL)
return -ENOMEM;
d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
debugfs_create_u32("taken_slow", 0444, d_spin_debug,
&spinlock_stats.contention_stats[TAKEN_SLOW]);
debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
&spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
debugfs_create_u32("released_slow", 0444, d_spin_debug,
&spinlock_stats.contention_stats[RELEASED_SLOW]);
debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
&spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
debugfs_create_u64("time_blocked", 0444, d_spin_debug,
&spinlock_stats.time_blocked);
debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
return 0;
}
fs_initcall(kvm_spinlock_debugfs);
#else /* !CONFIG_KVM_DEBUG_FS */
static inline void add_stats(enum kvm_contention_stat var, u32 val)
{
}
static inline u64 spin_time_start(void)
{
return 0;
}
static inline void spin_time_accum_blocked(u64 start)
{
}
#endif /* CONFIG_KVM_DEBUG_FS */
struct kvm_lock_waiting {
struct arch_spinlock *lock;
__ticket_t want;
};
/* cpus 'waiting' on a spinlock to become available */
static cpumask_t waiting_cpus;
/* Track spinlock on which a cpu is waiting */
static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
__visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
{
struct kvm_lock_waiting *w;
int cpu;
u64 start;
unsigned long flags;
__ticket_t head;
if (in_nmi())
return;
w = this_cpu_ptr(&klock_waiting);
cpu = smp_processor_id();
start = spin_time_start();
/*
* Make sure an interrupt handler can't upset things in a
* partially setup state.
*/
local_irq_save(flags);
/*
* The ordering protocol on this is that the "lock" pointer
* may only be set non-NULL if the "want" ticket is correct.
* If we're updating "want", we must first clear "lock".
*/
w->lock = NULL;
smp_wmb();
w->want = want;
smp_wmb();
w->lock = lock;
add_stats(TAKEN_SLOW, 1);
/*
* This uses set_bit, which is atomic but we should not rely on its
* reordering gurantees. So barrier is needed after this call.
*/
cpumask_set_cpu(cpu, &waiting_cpus);
barrier();
/*
* Mark entry to slowpath before doing the pickup test to make
* sure we don't deadlock with an unlocker.
*/
__ticket_enter_slowpath(lock);
/* make sure enter_slowpath, which is atomic does not cross the read */
smp_mb__after_atomic();
/*
* check again make sure it didn't become free while
* we weren't looking.
*/
head = READ_ONCE(lock->tickets.head);
if (__tickets_equal(head, want)) {
add_stats(TAKEN_SLOW_PICKUP, 1);
goto out;
}
/*
* halt until it's our turn and kicked. Note that we do safe halt
* for irq enabled case to avoid hang when lock info is overwritten
* in irq spinlock slowpath and no spurious interrupt occur to save us.
*/
if (arch_irqs_disabled_flags(flags))
halt();
else
safe_halt();
out:
cpumask_clear_cpu(cpu, &waiting_cpus);
w->lock = NULL;
local_irq_restore(flags);
spin_time_accum_blocked(start);
}
PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
/* Kick vcpu waiting on @lock->head to reach value @ticket */
static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
{
int cpu;
add_stats(RELEASED_SLOW, 1);
for_each_cpu(cpu, &waiting_cpus) {
const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
if (READ_ONCE(w->lock) == lock &&
READ_ONCE(w->want) == ticket) {
add_stats(RELEASED_SLOW_KICKED, 1);
kvm_kick_cpu(cpu);
break;
}
}
}
/*
* Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
*/
void __init kvm_spinlock_init(void)
{
if (!kvm_para_available())
return;
/* Does host kernel support KVM_FEATURE_PV_UNHALT? */
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
return;
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
pv_lock_ops.unlock_kick = kvm_unlock_kick;
}
static __init int kvm_spinlock_init_jump(void)
{
if (!kvm_para_available())
return 0;
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
return 0;
static_key_slow_inc(¶virt_ticketlocks_enabled);
printk(KERN_INFO "KVM setup paravirtual spinlock\n");
return 0;
}
early_initcall(kvm_spinlock_init_jump);
#endif /* CONFIG_PARAVIRT_SPINLOCKS */