4 files changed, 266 insertions, 11 deletions

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 7f1178f6b839..f63ccb0a5982 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -15,3 +15,6 @@ config KVM_APIC_ARCHITECTURE
 
 config KVM_MMIO
        bool
+
+config KVM_ASYNC_PF
+       bool
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
new file mode 100644
index 000000000000..857d63431cb7
--- /dev/null
+++ b/virt/kvm/async_pf.c
@@ -0,0 +1,190 @@
+/*
+ * kvm asynchronous fault support
+ *
+ * Copyright 2010 Red Hat, Inc.
+ *
+ * Author:
+ *      Gleb Natapov <gleb@redhat.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * 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,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mmu_context.h>
+
+#include "async_pf.h"
+#include <trace/events/kvm.h>
+
+static struct kmem_cache *async_pf_cache;
+
+int kvm_async_pf_init(void)
+{
+        async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
+
+        if (!async_pf_cache)
+                return -ENOMEM;
+
+        return 0;
+}
+
+void kvm_async_pf_deinit(void)
+{
+        if (async_pf_cache)
+                kmem_cache_destroy(async_pf_cache);
+        async_pf_cache = NULL;
+}
+
+void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
+{
+        INIT_LIST_HEAD(&vcpu->async_pf.done);
+        INIT_LIST_HEAD(&vcpu->async_pf.queue);
+        spin_lock_init(&vcpu->async_pf.lock);
+}
+
+static void async_pf_execute(struct work_struct *work)
+{
+        struct page *page = NULL;
+        struct kvm_async_pf *apf =
+                container_of(work, struct kvm_async_pf, work);
+        struct mm_struct *mm = apf->mm;
+        struct kvm_vcpu *vcpu = apf->vcpu;
+        unsigned long addr = apf->addr;
+        gva_t gva = apf->gva;
+
+        might_sleep();
+
+        use_mm(mm);
+        down_read(&mm->mmap_sem);
+        get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
+        up_read(&mm->mmap_sem);
+        unuse_mm(mm);
+
+        spin_lock(&vcpu->async_pf.lock);
+        list_add_tail(&apf->link, &vcpu->async_pf.done);
+        apf->page = page;
+        apf->done = true;
+        spin_unlock(&vcpu->async_pf.lock);
+
+        /*
+         * apf may be freed by kvm_check_async_pf_completion() after
+         * this point
+         */
+
+        trace_kvm_async_pf_completed(addr, page, gva);
+
+        if (waitqueue_active(&vcpu->wq))
+                wake_up_interruptible(&vcpu->wq);
+
+        mmdrop(mm);
+        kvm_put_kvm(vcpu->kvm);
+}
+
+void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
+{
+        /* cancel outstanding work queue item */
+        while (!list_empty(&vcpu->async_pf.queue)) {
+                struct kvm_async_pf *work =
+                        list_entry(vcpu->async_pf.queue.next,
+                                   typeof(*work), queue);
+                cancel_work_sync(&work->work);
+                list_del(&work->queue);
+                if (!work->done) /* work was canceled */
+                        kmem_cache_free(async_pf_cache, work);
+        }
+
+        spin_lock(&vcpu->async_pf.lock);
+        while (!list_empty(&vcpu->async_pf.done)) {
+                struct kvm_async_pf *work =
+                        list_entry(vcpu->async_pf.done.next,
+                                   typeof(*work), link);
+                list_del(&work->link);
+                if (work->page)
+                        put_page(work->page);
+                kmem_cache_free(async_pf_cache, work);
+        }
+        spin_unlock(&vcpu->async_pf.lock);
+
+        vcpu->async_pf.queued = 0;
+}
+
+void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
+{
+        struct kvm_async_pf *work;
+
+        if (list_empty_careful(&vcpu->async_pf.done))
+                return;
+
+        spin_lock(&vcpu->async_pf.lock);
+        work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
+        list_del(&work->link);
+        spin_unlock(&vcpu->async_pf.lock);
+
+        kvm_arch_async_page_present(vcpu, work);
+
+        list_del(&work->queue);
+        vcpu->async_pf.queued--;
+        if (work->page)
+                put_page(work->page);
+        kmem_cache_free(async_pf_cache, work);
+}
+
+int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
+                       struct kvm_arch_async_pf *arch)
+{
+        struct kvm_async_pf *work;
+
+        if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
+                return 0;
+
+        /* setup delayed work */
+
+        /*
+         * do alloc nowait since if we are going to sleep anyway we
+         * may as well sleep faulting in page
+         */
+        work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
+        if (!work)
+                return 0;
+
+        work->page = NULL;
+        work->done = false;
+        work->vcpu = vcpu;
+        work->gva = gva;
+        work->addr = gfn_to_hva(vcpu->kvm, gfn);
+        work->arch = *arch;
+        work->mm = current->mm;
+        atomic_inc(&work->mm->mm_count);
+        kvm_get_kvm(work->vcpu->kvm);
+
+        /* this can't really happen otherwise gfn_to_pfn_async
+           would succeed */
+        if (unlikely(kvm_is_error_hva(work->addr)))
+                goto retry_sync;
+
+        INIT_WORK(&work->work, async_pf_execute);
+        if (!schedule_work(&work->work))
+                goto retry_sync;
+
+        list_add_tail(&work->queue, &vcpu->async_pf.queue);
+        vcpu->async_pf.queued++;
+        kvm_arch_async_page_not_present(vcpu, work);
+        return 1;
+retry_sync:
+        kvm_put_kvm(work->vcpu->kvm);
+        mmdrop(work->mm);
+        kmem_cache_free(async_pf_cache, work);
+        return 0;
+}
diff --git a/virt/kvm/async_pf.h b/virt/kvm/async_pf.h
new file mode 100644
index 000000000000..e7ef6447cb82
--- /dev/null
+++ b/virt/kvm/async_pf.h
@@ -0,0 +1,36 @@
+/*
+ * kvm asynchronous fault support
+ *
+ * Copyright 2010 Red Hat, Inc.
+ *
+ * Author:
+ *      Gleb Natapov <gleb@redhat.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * 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,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __KVM_ASYNC_PF_H__
+#define __KVM_ASYNC_PF_H__
+
+#ifdef CONFIG_KVM_ASYNC_PF
+int kvm_async_pf_init(void);
+void kvm_async_pf_deinit(void);
+void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu);
+#else
+#define kvm_async_pf_init() (0)
+#define kvm_async_pf_deinit() do{}while(0)
+#define kvm_async_pf_vcpu_init(C) do{}while(0)
+#endif
+
+#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5225052aebc1..75fd590c0214 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -55,6 +55,7 @@
 #include <asm-generic/bitops/le.h>
 
 #include "coalesced_mmio.h"
+#include "async_pf.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/kvm.h>
@@ -186,6 +187,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
         vcpu->kvm = kvm;
         vcpu->vcpu_id = id;
         init_waitqueue_head(&vcpu->wq);
+        kvm_async_pf_vcpu_init(vcpu);
 
         page = alloc_page(GFP_KERNEL | __GFP_ZERO);
         if (!page) {
@@ -946,15 +948,20 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
-static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
+static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
+                        bool *async)
 {
         struct page *page[1];
-        int npages;
+        int npages = 0;
         pfn_t pfn;
 
-        if (atomic)
+        /* we can do it either atomically or asynchronously, not both */
+        BUG_ON(atomic && async);
+
+        if (atomic || async)
                 npages = __get_user_pages_fast(addr, 1, 1, page);
-        else {
+
+        if (unlikely(npages != 1) && !atomic) {
                 might_sleep();
                 npages = get_user_pages_fast(addr, 1, 1, page);
         }
@@ -976,6 +983,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
 
                 if (vma == NULL || addr < vma->vm_start ||
                     !(vma->vm_flags & VM_PFNMAP)) {
+                        if (async && !(vma->vm_flags & VM_PFNMAP) &&
+                            (vma->vm_flags & VM_WRITE))
+                                *async = true;
                         up_read(&current->mm->mmap_sem);
 return_fault_page:
                         get_page(fault_page);
@@ -993,32 +1003,41 @@ return_fault_page:
 
 pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr)
 {
-        return hva_to_pfn(kvm, addr, true);
+        return hva_to_pfn(kvm, addr, true, NULL);
 }
 EXPORT_SYMBOL_GPL(hva_to_pfn_atomic);
 
-static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic)
+static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async)
 {
         unsigned long addr;
 
+        if (async)
+                *async = false;
+
         addr = gfn_to_hva(kvm, gfn);
         if (kvm_is_error_hva(addr)) {
                 get_page(bad_page);
                 return page_to_pfn(bad_page);
         }
 
-        return hva_to_pfn(kvm, addr, atomic);
+        return hva_to_pfn(kvm, addr, atomic, async);
 }
 
 pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
 {
-        return __gfn_to_pfn(kvm, gfn, true);
+        return __gfn_to_pfn(kvm, gfn, true, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_atomic);
 
+pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async)
+{
+        return __gfn_to_pfn(kvm, gfn, false, async);
+}
+EXPORT_SYMBOL_GPL(gfn_to_pfn_async);
+
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
 {
-        return __gfn_to_pfn(kvm, gfn, false);
+        return __gfn_to_pfn(kvm, gfn, false, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn);
 
@@ -1026,7 +1045,7 @@ pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
                          struct kvm_memory_slot *slot, gfn_t gfn)
 {
         unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-        return hva_to_pfn(kvm, addr, false);
+        return hva_to_pfn(kvm, addr, false, NULL);
 }
 
 int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
@@ -2336,6 +2355,10 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
                 goto out_free_5;
         }
 
+        r = kvm_async_pf_init();
+        if (r)
+                goto out_free;
+
         kvm_chardev_ops.owner = module;
         kvm_vm_fops.owner = module;
         kvm_vcpu_fops.owner = module;
@@ -2343,7 +2366,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
         r = misc_register(&kvm_dev);
         if (r) {
                 printk(KERN_ERR "kvm: misc device register failed\n");
-                goto out_free;
+                goto out_unreg;
         }
 
         kvm_preempt_ops.sched_in = kvm_sched_in;
@@ -2353,6 +2376,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 
         return 0;
 
+out_unreg:
+        kvm_async_pf_deinit();
 out_free:
         kmem_cache_destroy(kvm_vcpu_cache);
 out_free_5:
@@ -2385,6 +2410,7 @@ void kvm_exit(void)
         kvm_exit_debug();
         misc_deregister(&kvm_dev);
         kmem_cache_destroy(kvm_vcpu_cache);
+        kvm_async_pf_deinit();
         sysdev_unregister(&kvm_sysdev);
         sysdev_class_unregister(&kvm_sysdev_class);
         unregister_reboot_notifier(&kvm_reboot_notifier);