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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: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-07-29 12:31:15 +02:00
parent dd489240a2
commit 71ba994c94
3 changed files with 15 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
arch/x86/kvm/i8259.c
View File

@ -651,15 +651,10 @@ fail_unlock:
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;
kfree(vpic);
}
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);
}

8
arch/x86/kvm/irq.h
View File

@ -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);

17
arch/x86/kvm/x86.c
View File

@ -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;