[RFC PATCH 1/3] VFIO: Add new cmd to receive eventfd from userspace to notify IOMMU fault event

[Lan Tianyu <tianyu.lan@intel.com>]

This patch is to receive IOMMU fault eventfd and IOMMU fault event flag
from userspace. VFIO should register IOMMU fault event handler according
fault event flag which designates what kind of fault events need to be
reported.  When VFIO get IOMMU fault event from IOMMU driver, it should
notify userspace via received fd.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
---
 drivers/vfio/vfio_iommu_type1.c | 45 +++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h       | 15 ++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index b3cc33f..46674ea 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -38,6 +38,7 @@
 #include <linux/workqueue.h>
 #include <linux/mdev.h>
 #include <linux/notifier.h>
+#include <linux/eventfd.h>
 
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
@@ -61,6 +62,8 @@ struct vfio_iommu {
 	struct mutex		lock;
 	struct rb_root		dma_list;
 	struct blocking_notifier_head notifier;
+	struct eventfd_ctx	*iommu_fault_fd;
+	struct mutex            fault_lock;
 	bool			v2;
 	bool			nesting;
 };
@@ -1452,6 +1455,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 	INIT_LIST_HEAD(&iommu->domain_list);
 	iommu->dma_list = RB_ROOT;
 	mutex_init(&iommu->lock);
+	mutex_init(&iommu->fault_lock);
 	BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
 
 	return iommu;
@@ -1582,6 +1586,47 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		return copy_to_user((void __user *)arg, &unmap, minsz) ?
 			-EFAULT : 0;
+	} else if (cmd == VFIO_IOMMU_SET_FAULT_EVENTFD) {
+		struct vfio_iommu_type1_set_fault_eventfd eventfd;
+		int fd;
+		int ret;
+
+		minsz = offsetofend(struct vfio_iommu_type1_set_fault_eventfd,
+				    fd);
+
+		if (copy_from_user(&eventfd, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (eventfd.argsz < minsz)
+			return -EINVAL;
+
+
+		mutex_lock(&iommu->fault_lock);
+
+		fd = eventfd.fd;
+		if (fd == -1) {
+			if (iommu->iommu_fault_fd)
+				eventfd_ctx_put(iommu->iommu_fault_fd);
+			iommu->iommu_fault_fd = NULL;
+			ret = 0;
+		} else if (fd >= 0) {
+			struct eventfd_ctx *ctx;
+
+			ctx = eventfd_ctx_fdget(fd);
+			if (IS_ERR(ctx))
+				return PTR_ERR(ctx);
+
+			if (ctx)
+				eventfd_ctx_put(ctx);
+
+			iommu->iommu_fault_fd = ctx;
+			ret = 0;
+		} else
+			ret = -EINVAL;
+
+		mutex_unlock(&iommu->fault_lock);
+
+		return ret;
 	}
 
 	return -ENOTTY;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 519eff3..8616334 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -547,6 +547,21 @@ struct vfio_iommu_type1_dma_unmap {
 #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
 #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+/*
+ * VFIO_IOMMU_SET_FAULT_EVENT_FD	_IO(VFIO_TYPE, VFIO_BASE + 17)
+ *
+ * Receive eventfd from userspace to notify fault event from IOMMU.
+ */
+struct vfio_iommu_type1_set_fault_eventfd {
+	__u32	argsz;
+	__u32   flags;
+/* What IOMMU Fault events should be reported. */
+#define VFIO_IOMMU_UR_FAULT_WITHOUT_PASID (1 << 0)
+	__s32	fd;			/* Eventfd from user space */
+};
+
+#define VFIO_IOMMU_SET_FAULT_EVENTFD	_IO(VFIO_TYPE, VFIO_BASE + 17)
+
 /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
 
 /*
-- 
1.8.3.1