1 files changed, 181 insertions, 0 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 032d03b6b54a..d5640634fef6 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -29,8 +29,14 @@
 #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 <asm/timer.h>
 #include <asm/cpu.h>
+#include <asm/traps.h>
+#include <asm/desc.h>
 
 #define MMU_QUEUE_SIZE 1024
 
@@ -64,6 +70,168 @@ 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;
+};
+
+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);
+
+        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);
+                return;
+        }
+
+        n.token = token;
+        n.cpu = smp_processor_id();
+        init_waitqueue_head(&n.wq);
+        hlist_add_head(&n.link, &b->list);
+        spin_unlock(&b->lock);
+
+        for (;;) {
+                prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
+                if (hlist_unhashed(&n.link))
+                        break;
+                local_irq_enable();
+                schedule();
+                local_irq_disable();
+        }
+        finish_wait(&n.wq, &wait);
+
+        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 (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 = kmalloc(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 (__get_cpu_var(apf_reason).enabled) {
+                reason = __get_cpu_var(apf_reason).reason;
+                __get_cpu_var(apf_reason).reason = 0;
+        }
+
+        return reason;
+}
+EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
+
+dotraplinkage void __kprobes
+do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+        switch (kvm_read_and_reset_pf_reason()) {
+        default:
+                do_page_fault(regs, error_code);
+                break;
+        case KVM_PV_REASON_PAGE_NOT_PRESENT:
+                /* page is swapped out by the host. */
+                kvm_async_pf_task_wait((u32)read_cr2());
+                break;
+        case KVM_PV_REASON_PAGE_READY:
+                kvm_async_pf_task_wake((u32)read_cr2());
+                break;
+        }
+}
+
 static void kvm_mmu_op(void *buffer, unsigned len)
 {
         int r;
@@ -300,6 +468,7 @@ static void kvm_guest_cpu_online(void *dummy)
 static void kvm_guest_cpu_offline(void *dummy)
 {
         kvm_pv_disable_apf(NULL);
+        apf_task_wake_all();
 }
 
 static int __cpuinit kvm_cpu_notify(struct notifier_block *self,
@@ -327,13 +496,25 @@ static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
 };
 #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;
+
 #ifdef CONFIG_SMP
         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
         register_cpu_notifier(&kvm_cpu_notifier);