vfio: Register/unregister irq_bypass_producer

This patch adds the registration/unregistration of an
irq_bypass_producer for MSI/MSIx on vfio pci devices.

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Feng Wu <feng.wu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index 4540179..850d86c 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -33,3 +33,4 @@
 
 source "drivers/vfio/pci/Kconfig"
 source "drivers/vfio/platform/Kconfig"
+source "virt/lib/Kconfig"
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 579d83b..02912f1 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -2,6 +2,7 @@
 	tristate "VFIO support for PCI devices"
 	depends on VFIO && PCI && EVENTFD
 	select VFIO_VIRQFD
+	select IRQ_BYPASS_MANAGER
 	help
 	  Support for the PCI VFIO bus driver.  This is required to make
 	  use of PCI drivers using the VFIO framework.
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 1f577b4..3b3ba15 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -319,6 +319,7 @@
 
 	if (vdev->ctx[vector].trigger) {
 		free_irq(irq, vdev->ctx[vector].trigger);
+		irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
 		kfree(vdev->ctx[vector].name);
 		eventfd_ctx_put(vdev->ctx[vector].trigger);
 		vdev->ctx[vector].trigger = NULL;
@@ -360,6 +361,14 @@
 		return ret;
 	}
 
+	vdev->ctx[vector].producer.token = trigger;
+	vdev->ctx[vector].producer.irq = irq;
+	ret = irq_bypass_register_producer(&vdev->ctx[vector].producer);
+	if (unlikely(ret))
+		dev_info(&pdev->dev,
+		"irq bypass producer (token %p) registration fails: %d\n",
+		vdev->ctx[vector].producer.token, ret);
+
 	vdev->ctx[vector].trigger = trigger;
 
 	return 0;
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index ae0e1b4..0e7394f 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -13,6 +13,7 @@
 
 #include <linux/mutex.h>
 #include <linux/pci.h>
+#include <linux/irqbypass.h>
 
 #ifndef VFIO_PCI_PRIVATE_H
 #define VFIO_PCI_PRIVATE_H
@@ -29,6 +30,7 @@
 	struct virqfd		*mask;
 	char			*name;
 	bool			masked;
+	struct irq_bypass_producer	producer;
 };
 
 struct vfio_pci_device {