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Commit 71ba994c authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: clean/fix memory barriers in irqchip_in_kernel 



The memory barriers are trying to protect against concurrent RCU-based
interrupt injection, but the IRQ routing table is not valid at the time
kvm->arch.vpic is written.  Fix this by writing kvm->arch.vpic last.
kvm_destroy_pic then need not set kvm->arch.vpic to NULL; modify it
to take a struct kvm_pic* and reuse it if the IOAPIC creation fails.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent dd489240

arch/x86/kvm/i8259.c

+5 −10
Original line number Diff line number Diff line
@@ -651,15 +651,10 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm) 
	return NULL;

}



void kvm_destroy_pic(struct kvm *kvm)

void kvm_destroy_pic(struct kvm_pic *vpic)

{

	struct kvm_pic *vpic = kvm->arch.vpic;



	if (vpic) {

		kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &vpic->dev_master);

		kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &vpic->dev_slave);

		kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &vpic->dev_eclr);

		kvm->arch.vpic = NULL;

	kvm_io_bus_unregister_dev(vpic->kvm, KVM_PIO_BUS, &vpic->dev_master);

	kvm_io_bus_unregister_dev(vpic->kvm, KVM_PIO_BUS, &vpic->dev_slave);

	kvm_io_bus_unregister_dev(vpic->kvm, KVM_PIO_BUS, &vpic->dev_eclr);

	kfree(vpic);

}
 
}

arch/x86/kvm/irq.h

+4 −4
Original line number Diff line number Diff line
@@ -74,7 +74,7 @@ struct kvm_pic { 
};



struct kvm_pic *kvm_create_pic(struct kvm *kvm);

void kvm_destroy_pic(struct kvm *kvm);

void kvm_destroy_pic(struct kvm_pic *vpic);

int kvm_pic_read_irq(struct kvm *kvm);

void kvm_pic_update_irq(struct kvm_pic *s);
@@ -85,11 +85,11 @@ static inline struct kvm_pic *pic_irqchip(struct kvm *kvm) 


static inline int irqchip_in_kernel(struct kvm *kvm)

{

	int ret;

	struct kvm_pic *vpic = pic_irqchip(kvm);



	ret = (pic_irqchip(kvm) != NULL);

	/* Read vpic before kvm->irq_routing.  */

	smp_rmb();

	return ret;

	return vpic != NULL;

}



void kvm_pic_reset(struct kvm_kpic_state *s);

arch/x86/kvm/x86.c

+6 −11
Original line number Diff line number Diff line
@@ -3626,30 +3626,25 @@ long kvm_arch_vm_ioctl(struct file *filp, 
			r = kvm_ioapic_init(kvm);

			if (r) {

				mutex_lock(&kvm->slots_lock);

				kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,

							  &vpic->dev_master);

				kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,

							  &vpic->dev_slave);

				kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,

							  &vpic->dev_eclr);

				kvm_destroy_pic(vpic);

				mutex_unlock(&kvm->slots_lock);

				kfree(vpic);

				goto create_irqchip_unlock;

			}

		} else

			goto create_irqchip_unlock;

		smp_wmb();

		kvm->arch.vpic = vpic;

		smp_wmb();

		r = kvm_setup_default_irq_routing(kvm);

		if (r) {

			mutex_lock(&kvm->slots_lock);

			mutex_lock(&kvm->irq_lock);

			kvm_ioapic_destroy(kvm);

			kvm_destroy_pic(kvm);

			kvm_destroy_pic(vpic);

			mutex_unlock(&kvm->irq_lock);

			mutex_unlock(&kvm->slots_lock);

			goto create_irqchip_unlock;

		}

		/* Write kvm->irq_routing before kvm->arch.vpic.  */

		smp_wmb();

		kvm->arch.vpic = vpic;

	create_irqchip_unlock:

		mutex_unlock(&kvm->lock);

		break;