[RFC v3 10/15] vfio: allow the user to register reserved iova range for MSI mapping

[Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

The user is allowed to register a reserved IOVA range by using the
DMA MAP API and setting the new flag: VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA.
It provides the base address and the size. This region is stored in the
vfio_dma rb tree. At that point the iova range is not mapped to any target
address yet. The host kernel will use those iova when needed, typically
when the VFIO-PCI device allocates its MSI's.

This patch also handles the destruction of the reserved binding RB-tree and
domain's iova_domains.

Signed-off-by: Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Signed-off-by: Bharat Bhushan <Bharat.Bhushan-KZfg59tc24xl57MIdRCFDg@public.gmane.org>

---

v1 -> v2:
- set returned value according to alloc_reserved_iova_domain result
- free the iova domains in case any error occurs

RFC v1 -> v1:
- takes into account Alex comments, based on
  [RFC PATCH 1/6] vfio: Add interface for add/del reserved iova region:
- use the existing dma map/unmap ioctl interface with a flag to register
  a reserved IOVA range. A single reserved iova region is allowed.
---
 drivers/vfio/vfio_iommu_type1.c | 75 ++++++++++++++++++++++++++++++++++++++++-
 include/uapi/linux/vfio.h       |  9 +++++
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index b9326c9..c5d3b48 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -673,6 +673,75 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	return ret;
 }
 
+static int vfio_register_reserved_iova_range(struct vfio_iommu *iommu,
+			   struct vfio_iommu_type1_dma_map *map)
+{
+	dma_addr_t iova = map->iova;
+	size_t size = map->size;
+	uint64_t mask;
+	struct vfio_dma *dma;
+	int ret = 0;
+	struct vfio_domain *d;
+	unsigned long order;
+
+	/* Verify that none of our __u64 fields overflow */
+	if (map->size != size || map->iova != iova)
+		return -EINVAL;
+
+	order =  __ffs(vfio_pgsize_bitmap(iommu));
+	mask = ((uint64_t)1 << order) - 1;
+
+	WARN_ON(mask & PAGE_MASK);
+
+	/* we currently only support MSI_RESERVED_IOVA */
+	if (!(map->flags & VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA))
+		return -EINVAL;
+
+	if (!size || (size | iova) & mask)
+		return -EINVAL;
+
+	/* Don't allow IOVA address wrap */
+	if (iova + size - 1 < iova)
+		return -EINVAL;
+
+	mutex_lock(&iommu->lock);
+
+	/* check if the iova domain has not been instantiated already*/
+	d = list_first_entry(&iommu->domain_list,
+				  struct vfio_domain, next);
+
+	if (vfio_find_dma(iommu, iova, size)) {
+		ret =  -EEXIST;
+		goto out;
+	}
+
+	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
+	if (!dma) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dma->iova = iova;
+	dma->size = size;
+	dma->type = VFIO_IOVA_RESERVED;
+
+	list_for_each_entry(d, &iommu->domain_list, next)
+		ret |= iommu_alloc_reserved_iova_domain(d->domain, iova,
+							size, order);
+
+	if (ret) {
+		list_for_each_entry(d, &iommu->domain_list, next)
+			iommu_free_reserved_iova_domain(d->domain);
+		goto out;
+	}
+
+	vfio_link_dma(iommu, dma);
+
+out:
+	mutex_unlock(&iommu->lock);
+	return ret;
+}
+
 static int vfio_bus_type(struct device *dev, void *data)
 {
 	struct bus_type **bus = data;
@@ -1045,7 +1114,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 	} else if (cmd == VFIO_IOMMU_MAP_DMA) {
 		struct vfio_iommu_type1_dma_map map;
 		uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
-				VFIO_DMA_MAP_FLAG_WRITE;
+				VFIO_DMA_MAP_FLAG_WRITE |
+				VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA;
 
 		minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);
 
@@ -1055,6 +1125,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		if (map.argsz < minsz || map.flags & ~mask)
 			return -EINVAL;
 
+		if (map.flags & VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA)
+			return vfio_register_reserved_iova_range(iommu, &map);
+
 		return vfio_dma_do_map(iommu, &map);
 
 	} else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 43e183b..982e326 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -411,12 +411,21 @@ struct vfio_iommu_type1_info {
  *
  * Map process virtual addresses to IO virtual addresses using the
  * provided struct vfio_dma_map. Caller sets argsz. READ &/ WRITE required.
+ *
+ * In case MSI_RESERVED_IOVA is set, the API only aims at registering an IOVA
+ * region which will be used on some platforms to map the host MSI frame.
+ * in that specific case, vaddr and prot are ignored. The requirement for
+ * provisioning such IOVA range can be checked by calling VFIO_IOMMU_GET_INFO
+ * with the VFIO_IOMMU_INFO_REQUIRE_MSI_MAP attribute. A single
+ * MSI_RESERVED_IOVA region can be registered
  */
 struct vfio_iommu_type1_dma_map {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_DMA_MAP_FLAG_READ (1 << 0)		/* readable from device */
 #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1)	/* writable from device */
+/* reserved iova for MSI vectors*/
+#define VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA (1 << 2)
 	__u64	vaddr;				/* Process virtual address */
 	__u64	iova;				/* IO virtual address */
 	__u64	size;				/* Size of mapping (bytes) */
-- 
1.9.1