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x86/PCI: VMD: Synchronize with RCU freeing MSI IRQ descs

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Fix a potential race when disabling MSI/MSI-X on a VMD domain device.  If
the VMD interrupt service is running, it may see a disabled IRQ.  We can
synchronize RCU just before freeing the MSI descriptor.  This is safe since
the irq_desc lock isn't held, and the descriptor is valid even though it is
disabled.  After vmd_msi_free(), though, the handler is reinitialized to
handle_bad_irq(), so we can't let the VMD ISR's list iteration see the
disabled IRQ after this.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by Jon Derrick: <jonathan.derrick@intel.com>
This commit is contained in:
Keith Busch 2016-08-04 16:09:09 -06:00 committed by Bjorn Helgaas
parent b31822277a
commit ee6ee49fd0
1 changed files with 2 additions and 0 deletions
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2
arch/x86/pci/vmd.c
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@ -218,6 +218,8 @@ static void vmd_msi_free(struct irq_domain *domain,
struct vmd_irq *vmdirq = irq_get_chip_data(virq);
unsigned long flags;
synchronize_rcu();
/* XXX: Potential optimization to rebalance */
raw_spin_lock_irqsave(&list_lock, flags);
vmdirq->irq->count--;