vfio/pci: Add ioeventfd support

The ioeventfd here is actually irqfd handling of an ioeventfd such as
supported in KVM.  A user is able to pre-program a device write to
occur when the eventfd triggers.  This is yet another instance of
eventfd-irqfd triggering between KVM and vfio.  The impetus for this
is high frequency writes to pages which are virtualized in QEMU.
Enabling this near-direct write path for selected registers within
the virtualized page can improve performance and reduce overhead.
Specifically this is initially targeted at NVIDIA graphics cards where
the driver issues a write to an MMIO register within a virtualized
region in order to allow the MSI interrupt to re-trigger.

Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index f561ac1c78a0..cde3b5d3441a 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -29,6 +29,19 @@
 #define PCI_CAP_ID_INVALID		0xFF	/* default raw access */
 #define PCI_CAP_ID_INVALID_VIRT		0xFE	/* default virt access */
 
+/* Cap maximum number of ioeventfds per device (arbitrary) */
+#define VFIO_PCI_IOEVENTFD_MAX		1000
+
+struct vfio_pci_ioeventfd {
+	struct list_head	next;
+	struct virqfd		*virqfd;
+	void __iomem		*addr;
+	uint64_t		data;
+	loff_t			pos;
+	int			bar;
+	int			count;
+};
+
 struct vfio_pci_irq_ctx {
 	struct eventfd_ctx	*trigger;
 	struct virqfd		*unmask;
@@ -92,9 +105,12 @@ struct vfio_pci_device {
 	bool			nointx;
 	struct pci_saved_state	*pci_saved_state;
 	int			refcnt;
+	int			ioeventfds_nr;
 	struct eventfd_ctx	*err_trigger;
 	struct eventfd_ctx	*req_trigger;
 	struct list_head	dummy_resources_list;
+	struct mutex		ioeventfds_lock;
+	struct list_head	ioeventfds_list;
 };
 
 #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)
@@ -120,6 +136,9 @@ extern ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
 extern ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
 			       size_t count, loff_t *ppos, bool iswrite);
 
+extern long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
+			       uint64_t data, int count, int fd);
+
 extern int vfio_pci_init_perm_bits(void);
 extern void vfio_pci_uninit_perm_bits(void);