[PATCH v9 04/11] vfio/pci: Add VFIO_REGION_TYPE_NESTED region type

[Eric Auger]

Add a new specific DMA_FAULT region aiming to exposed nested mode
translation faults.

The region has a ring buffer that contains the actual fault
records plus a header allowing to handle it (tail/head indices,
max capacity, entry size). At the moment the region is dimensionned
for 512 fault records.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>

---

v8 -> v9:
- Use a single region instead of a prod/cons region

v4 -> v5
- check cons is not null in vfio_pci_check_cons_fault

v3 -> v4:
- use 2 separate regions, respectively in read and write modes
- add the version capability
---
 drivers/vfio/pci/vfio_pci.c         | 68 +++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_private.h | 10 +++++
 drivers/vfio/pci/vfio_pci_rdwr.c    | 45 +++++++++++++++++++
 include/uapi/linux/vfio.h           | 35 +++++++++++++++
 4 files changed, 158 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 703948c9fbe1..3b091cfdaf46 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -258,6 +258,69 @@ int vfio_pci_set_power_state(struct vfio_pci_device *vdev, pci_power_t state)
 	return ret;
 }
 
+static void vfio_pci_dma_fault_release(struct vfio_pci_device *vdev,
+				       struct vfio_pci_region *region)
+{
+}
+
+static int vfio_pci_dma_fault_add_capability(struct vfio_pci_device *vdev,
+					     struct vfio_pci_region *region,
+					     struct vfio_info_cap *caps)
+{
+	struct vfio_region_info_cap_fault cap = {
+		.header.id = VFIO_REGION_INFO_CAP_DMA_FAULT,
+		.header.version = 1,
+		.version = 1,
+	};
+	return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
+}
+
+static const struct vfio_pci_regops vfio_pci_dma_fault_regops = {
+	.rw		= vfio_pci_dma_fault_rw,
+	.release	= vfio_pci_dma_fault_release,
+	.add_capability = vfio_pci_dma_fault_add_capability,
+};
+
+#define DMA_FAULT_RING_LENGTH 512
+
+static int vfio_pci_init_dma_fault_region(struct vfio_pci_device *vdev)
+{
+	struct vfio_region_dma_fault *header;
+	size_t size;
+	int ret;
+
+	mutex_init(&vdev->fault_queue_lock);
+
+	/*
+	 * We provision 1 page for the header and space for
+	 * DMA_FAULT_RING_LENGTH fault records in the ring buffer.
+	 */
+	size = ALIGN(sizeof(struct iommu_fault) *
+		     DMA_FAULT_RING_LENGTH, PAGE_SIZE) + PAGE_SIZE;
+
+	vdev->fault_pages = kzalloc(size, GFP_KERNEL);
+	if (!vdev->fault_pages)
+		return -ENOMEM;
+
+	ret = vfio_pci_register_dev_region(vdev,
+		VFIO_REGION_TYPE_NESTED,
+		VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT,
+		&vfio_pci_dma_fault_regops, size,
+		VFIO_REGION_INFO_FLAG_READ | VFIO_REGION_INFO_FLAG_WRITE,
+		vdev->fault_pages);
+	if (ret)
+		goto out;
+
+	header = (struct vfio_region_dma_fault *)vdev->fault_pages;
+	header->entry_size = sizeof(struct iommu_fault);
+	header->nb_entries = DMA_FAULT_RING_LENGTH;
+	header->offset = sizeof(struct vfio_region_dma_fault);
+	return 0;
+out:
+	kfree(vdev->fault_pages);
+	return ret;
+}
+
 static int vfio_pci_enable(struct vfio_pci_device *vdev)
 {
 	struct pci_dev *pdev = vdev->pdev;
@@ -356,6 +419,10 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
 		}
 	}
 
+	ret = vfio_pci_init_dma_fault_region(vdev);
+	if (ret)
+		goto disable_exit;
+
 	vfio_pci_probe_mmaps(vdev);
 
 	return 0;
@@ -1371,6 +1438,7 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 
 	vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
 	kfree(vdev->region);
+	kfree(vdev->fault_pages);
 	mutex_destroy(&vdev->ioeventfds_lock);
 
 	if (!disable_idle_d3)
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index ee6ee91718a4..fde40db3cd34 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -119,6 +119,8 @@ struct vfio_pci_device {
 	int			ioeventfds_nr;
 	struct eventfd_ctx	*err_trigger;
 	struct eventfd_ctx	*req_trigger;
+	u8			*fault_pages;
+	struct mutex		fault_queue_lock;
 	struct list_head	dummy_resources_list;
 	struct mutex		ioeventfds_lock;
 	struct list_head	ioeventfds_list;
@@ -150,6 +152,14 @@ extern ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
 extern long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
 			       uint64_t data, int count, int fd);
 
+struct vfio_pci_fault_abi {
+	u32 entry_size;
+};
+
+extern size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev,
+				    char __user *buf, size_t count,
+				    loff_t *ppos, bool iswrite);
+
 extern int vfio_pci_init_perm_bits(void);
 extern void vfio_pci_uninit_perm_bits(void);
 
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 0120d8324a40..829c5284c6be 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -274,6 +274,51 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
 	return done;
 }
 
+size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev, char __user *buf,
+			     size_t count, loff_t *ppos, bool iswrite)
+{
+	unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) - VFIO_PCI_NUM_REGIONS;
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	void *base = vdev->region[i].data;
+	int ret = -EFAULT;
+
+	if (pos >= vdev->region[i].size)
+		return -EINVAL;
+
+	count = min(count, (size_t)(vdev->region[i].size - pos));
+
+	mutex_lock(&vdev->fault_queue_lock);
+
+	if (iswrite) {
+		struct vfio_region_dma_fault *header =
+			(struct vfio_region_dma_fault *)base;
+		u32 new_tail;
+
+		if (pos != 0 || count != 4) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+
+		if (copy_from_user((void *)&new_tail, buf, count))
+			goto unlock;
+
+		if (new_tail > header->nb_entries) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+		header->tail = new_tail;
+	} else {
+		if (copy_to_user(buf, base + pos, count))
+			goto unlock;
+	}
+	*ppos += count;
+	ret = count;
+unlock:
+	mutex_unlock(&vdev->fault_queue_lock);
+	return ret;
+}
+
+
 static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
 {
 	struct vfio_pci_ioeventfd *ioeventfd = opaque;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index deadbd84f2cf..bec761edae9b 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -307,6 +307,9 @@ struct vfio_region_info_cap_type {
 #define VFIO_REGION_TYPE_GFX                    (1)
 #define VFIO_REGION_SUBTYPE_GFX_EDID            (1)
 
+#define VFIO_REGION_TYPE_NESTED			(2)
+#define VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT	(1)
+
 /**
  * struct vfio_region_gfx_edid - EDID region layout.
  *
@@ -701,6 +704,38 @@ struct vfio_device_ioeventfd {
 
 #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+
+/*
+ * Capability exposed by the DMA fault region
+ * @version: ABI version
+ */
+#define VFIO_REGION_INFO_CAP_DMA_FAULT	6
+
+struct vfio_region_info_cap_fault {
+	struct vfio_info_cap_header header;
+	__u32 version;
+};
+
+/*
+ * DMA Fault Region Layout
+ * @tail: index relative to the start of the ring buffer at which the
+ *        consumer finds the next item in the buffer
+ * @entry_size: fault ring buffer entry size in bytes
+ * @nb_entries: max capacity of the fault ring buffer
+ * @offset: ring buffer offset relative to the start of the region
+ * @head: index relative to the start of the ring buffer at which the
+ *        producer (kernel) inserts items into the buffers
+ */
+struct vfio_region_dma_fault {
+	/* Write-Only */
+	__u32   tail;
+	/* Read-Only */
+	__u32   entry_size;
+	__u32	nb_entries;
+	__u32	offset;
+	__u32   head;
+};
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**
-- 
2.20.1