1 files changed, 241 insertions, 0 deletions
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
new file mode 100644
index 000000000..b8aaa96b7
--- /dev/null
+++ b/virt/kvm/async_pf.c
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kvm asynchronous fault support
+ *
+ * Copyright 2010 Red Hat, Inc.
+ *
+ * Author:
+ *      Gleb Natapov <gleb@redhat.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mmu_context.h>
+#include <linux/sched/mm.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)
+{
+	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 kvm_async_pf *apf =
+		container_of(work, struct kvm_async_pf, work);
+	struct kvm_vcpu *vcpu = apf->vcpu;
+	struct mm_struct *mm = vcpu->kvm->mm;
+	unsigned long addr = apf->addr;
+	gpa_t cr2_or_gpa = apf->cr2_or_gpa;
+	int locked = 1;
+	bool first;
+
+	might_sleep();
+
+	/*
+	 * Attempt to pin the VM's host address space, and simply skip gup() if
+	 * acquiring a pin fail, i.e. if the process is exiting.  Note, KVM
+	 * holds a reference to its associated mm_struct until the very end of
+	 * kvm_destroy_vm(), i.e. the struct itself won't be freed before this
+	 * work item is fully processed.
+	 */
+	if (mmget_not_zero(mm)) {
+		mmap_read_lock(mm);
+		get_user_pages_remote(mm, addr, 1, FOLL_WRITE, NULL, &locked);
+		if (locked)
+			mmap_read_unlock(mm);
+		mmput(mm);
+	}
+
+	/*
+	 * Notify and kick the vCPU even if faulting in the page failed, e.g.
+	 * so that the vCPU can retry the fault synchronously.
+	 */
+	if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
+		kvm_arch_async_page_present(vcpu, apf);
+
+	spin_lock(&vcpu->async_pf.lock);
+	first = list_empty(&vcpu->async_pf.done);
+	list_add_tail(&apf->link, &vcpu->async_pf.done);
+	spin_unlock(&vcpu->async_pf.lock);
+
+	/*
+	 * The apf struct may be freed by kvm_check_async_pf_completion() as
+	 * soon as the lock is dropped.  Nullify it to prevent improper usage.
+	 */
+	apf = NULL;
+
+	if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
+		kvm_arch_async_page_present_queued(vcpu);
+
+	trace_kvm_async_pf_completed(addr, cr2_or_gpa);
+
+	__kvm_vcpu_wake_up(vcpu);
+}
+
+static void kvm_flush_and_free_async_pf_work(struct kvm_async_pf *work)
+{
+	/*
+	 * The async #PF is "done", but KVM must wait for the work item itself,
+	 * i.e. async_pf_execute(), to run to completion.  If KVM is a module,
+	 * KVM must ensure *no* code owned by the KVM (the module) can be run
+	 * after the last call to module_put().  Note, flushing the work item
+	 * is always required when the item is taken off the completion queue.
+	 * E.g. even if the vCPU handles the item in the "normal" path, the VM
+	 * could be terminated before async_pf_execute() completes.
+	 *
+	 * Wake all events skip the queue and go straight done, i.e. don't
+	 * need to be flushed (but sanity check that the work wasn't queued).
+	 */
+	if (work->wakeup_all)
+		WARN_ON_ONCE(work->work.func);
+	else
+		flush_work(&work->work);
+	kmem_cache_free(async_pf_cache, work);
+}
+
+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_first_entry(&vcpu->async_pf.queue,
+					 typeof(*work), queue);
+		list_del(&work->queue);
+
+#ifdef CONFIG_KVM_ASYNC_PF_SYNC
+		flush_work(&work->work);
+#else
+		if (cancel_work_sync(&work->work))
+			kmem_cache_free(async_pf_cache, work);
+#endif
+	}
+
+	spin_lock(&vcpu->async_pf.lock);
+	while (!list_empty(&vcpu->async_pf.done)) {
+		struct kvm_async_pf *work =
+			list_first_entry(&vcpu->async_pf.done,
+					 typeof(*work), link);
+		list_del(&work->link);
+
+		spin_unlock(&vcpu->async_pf.lock);
+		kvm_flush_and_free_async_pf_work(work);
+		spin_lock(&vcpu->async_pf.lock);
+	}
+	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;
+
+	while (!list_empty_careful(&vcpu->async_pf.done) &&
+	      kvm_arch_can_dequeue_async_page_present(vcpu)) {
+		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_ready(vcpu, work);
+		if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
+			kvm_arch_async_page_present(vcpu, work);
+
+		list_del(&work->queue);
+		vcpu->async_pf.queued--;
+		kvm_flush_and_free_async_pf_work(work);
+	}
+}
+
+/*
+ * Try to schedule a job to handle page fault asynchronously. Returns 'true' on
+ * success, 'false' on failure (page fault has to be handled synchronously).
+ */
+bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
+			unsigned long hva, struct kvm_arch_async_pf *arch)
+{
+	struct kvm_async_pf *work;
+
+	if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
+		return false;
+
+	/* Arch specific code should not do async PF in this case */
+	if (unlikely(kvm_is_error_hva(hva)))
+		return false;
+
+	/*
+	 * 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 false;
+
+	work->wakeup_all = false;
+	work->vcpu = vcpu;
+	work->cr2_or_gpa = cr2_or_gpa;
+	work->addr = hva;
+	work->arch = *arch;
+
+	INIT_WORK(&work->work, async_pf_execute);
+
+	list_add_tail(&work->queue, &vcpu->async_pf.queue);
+	vcpu->async_pf.queued++;
+	work->notpresent_injected = kvm_arch_async_page_not_present(vcpu, work);
+
+	schedule_work(&work->work);
+
+	return true;
+}
+
+int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
+{
+	struct kvm_async_pf *work;
+	bool first;
+
+	if (!list_empty_careful(&vcpu->async_pf.done))
+		return 0;
+
+	work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
+	if (!work)
+		return -ENOMEM;
+
+	work->wakeup_all = true;
+	INIT_LIST_HEAD(&work->queue); /* for list_del to work */
+
+	spin_lock(&vcpu->async_pf.lock);
+	first = list_empty(&vcpu->async_pf.done);
+	list_add_tail(&work->link, &vcpu->async_pf.done);
+	spin_unlock(&vcpu->async_pf.lock);
+
+	if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
+		kvm_arch_async_page_present_queued(vcpu);
+
+	vcpu->async_pf.queued++;
+	return 0;
+}