[v2 17/25] KVM: kvm-vfio: User API for VT-d Posted-Interrupts

[Feng Wu <feng.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

This patch adds and documents a new attribute
KVM_DEV_VFIO_DEVICE_POSTING_IRQ in KVM_DEV_VFIO_DEVICE group.
This new attribute is used for VT-d Posted-Interrupts.

When guest OS changes the interrupt configuration for an
assigned device, such as, MSI/MSIx data/address fields,
QEMU will use this IRQ attribute to tell KVM to update the
related IRTE according the VT-d Posted-Interrrupts Specification,
such as, the guest vector should be updated in the related IRTE.

Signed-off-by: Feng Wu <feng.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 Documentation/virtual/kvm/devices/vfio.txt |    9 +++++++++
 include/uapi/linux/kvm.h                   |   10 ++++++++++
 2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/devices/vfio.txt b/Documentation/virtual/kvm/devices/vfio.txt
index f7aff29..41e12b7 100644
--- a/Documentation/virtual/kvm/devices/vfio.txt
+++ b/Documentation/virtual/kvm/devices/vfio.txt
@@ -42,3 +42,12 @@ activated before VFIO_DEVICE_SET_IRQS has been called to trigger the IRQ
 or associate an eventfd to it. Unforwarding can only be called while the
 signaling has been disabled with VFIO_DEVICE_SET_IRQS. If this condition is
 not satisfied, the command returns an -EBUSY.
+
+  KVM_DEV_VFIO_DEVICE_POSTING_IRQ: Use posted interrtups mechanism to post
+                                   the IRQ to guests.
+For this attribute, kvm_device_attr.addr points to a kvm_vfio_dev_irq struct.
+
+When guest OS changes the interrupt configuration for an assigned device,
+such as, MSI/MSIx data/address fields, QEMU will use this IRQ attribute
+to tell KVM to update the related IRTE according the VT-d Posted-Interrrupts
+Specification, such as, the guest vector should be updated in the related IRTE.
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a269a42..7d98650 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -949,6 +949,7 @@ struct kvm_device_attr {
 #define  KVM_DEV_VFIO_DEVICE			2
 #define   KVM_DEV_VFIO_DEVICE_FORWARD_IRQ			1
 #define   KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ			2
+#define   KVM_DEV_VFIO_DEVICE_POSTING_IRQ			3
 
 enum kvm_device_type {
 	KVM_DEV_TYPE_FSL_MPIC_20	= 1,
@@ -973,6 +974,15 @@ struct kvm_arch_forwarded_irq {
 	__u32 gsi; /* gsi, ie. virtual IRQ number */
 };
 
+struct kvm_vfio_dev_irq {
+	__u32	argsz;
+	__u32	fd;		/* file descriptor of the VFIO device */
+	__u32	index;		/* VFIO device IRQ index */
+	__u32	start;
+	__u32	count;
+	__u32	gsi[];		/* gsi, ie. virtual IRQ number */
+};
+
 /*
  * ioctls for VM fds
  */
-- 
1.7.1