From 36343f6ea721e003ed11b48a6a05d77a255b3a62 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 26 Oct 2016 13:35:56 +0200 Subject: [PATCH] KVM: fix OOPS on flush_work The conversion done by commit 3706feacd007 ("KVM: Remove deprecated create_singlethread_workqueue") is broken. It flushes a single work item &irqfd->shutdown instead of all of them, and even worse if there is no irqfd on the list then you get a NULL pointer dereference. Revert the virt/kvm/eventfd.c part of that patch; to avoid the deprecated function, just allocate our own workqueue---it does not even have to be unbound---with alloc_workqueue. Fixes: 3706feacd007 Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini --- virt/kvm/eventfd.c | 22 +++++++++++++++++++--- virt/kvm/kvm_main.c | 6 ++++++ 2 files changed, 25 insertions(+), 3 deletions(-) diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index f397e9b20370..a29786dd9522 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -42,6 +42,7 @@ #ifdef CONFIG_HAVE_KVM_IRQFD +static struct workqueue_struct *irqfd_cleanup_wq; static void irqfd_inject(struct work_struct *work) @@ -167,7 +168,7 @@ irqfd_deactivate(struct kvm_kernel_irqfd *irqfd) list_del_init(&irqfd->list); - schedule_work(&irqfd->shutdown); + queue_work(irqfd_cleanup_wq, &irqfd->shutdown); } int __attribute__((weak)) kvm_arch_set_irq_inatomic( @@ -554,7 +555,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args) * so that we guarantee there will not be any more interrupts on this * gsi once this deassign function returns. */ - flush_work(&irqfd->shutdown); + flush_workqueue(irqfd_cleanup_wq); return 0; } @@ -591,7 +592,7 @@ kvm_irqfd_release(struct kvm *kvm) * Block until we know all outstanding shutdown jobs have completed * since we do not take a kvm* reference. */ - flush_work(&irqfd->shutdown); + flush_workqueue(irqfd_cleanup_wq); } @@ -621,8 +622,23 @@ void kvm_irq_routing_update(struct kvm *kvm) spin_unlock_irq(&kvm->irqfds.lock); } +/* + * create a host-wide workqueue for issuing deferred shutdown requests + * aggregated from all vm* instances. We need our own isolated + * queue to ease flushing work items when a VM exits. + */ +int kvm_irqfd_init(void) +{ + irqfd_cleanup_wq = alloc_workqueue("kvm-irqfd-cleanup", 0, 0); + if (!irqfd_cleanup_wq) + return -ENOMEM; + + return 0; +} + void kvm_irqfd_exit(void) { + destroy_workqueue(irqfd_cleanup_wq); } #endif diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 28510e72618a..d92c3d5b0fbe 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3846,7 +3846,12 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, * kvm_arch_init makes sure there's at most one caller * for architectures that support multiple implementations, * like intel and amd on x86. + * kvm_arch_init must be called before kvm_irqfd_init to avoid creating + * conflicts in case kvm is already setup for another implementation. */ + r = kvm_irqfd_init(); + if (r) + goto out_irqfd; if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) { r = -ENOMEM; @@ -3928,6 +3933,7 @@ out_free_0a: free_cpumask_var(cpus_hardware_enabled); out_free_0: kvm_irqfd_exit(); +out_irqfd: kvm_arch_exit(); out_fail: return r; -- 2.20.1