[PATCH kernel v2 7/7] vfio/spapr_tce: Advertise and allow a huge DMA windows at 4GB

[Alexey Kardashevskiy <aik@ozlabs.ru>]

So far the only option for a big 64big DMA window was a window located
at 0x800.0000.0000.0000 (1<<59) which creates problems for devices
supporting smaller DMA masks.

This exploits a POWER9 PHB option to allow the second DMA window to map
at 0 and advertises it with a 4GB offset to avoid overlap with
the default 32bit window.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 include/uapi/linux/vfio.h           |  2 ++
 drivers/vfio/vfio_iommu_spapr_tce.c | 13 +++++++------
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 9e843a147ead..c7f89d47335a 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -831,9 +831,11 @@ struct vfio_iommu_spapr_tce_info {
 	__u32 argsz;
 	__u32 flags;
 #define VFIO_IOMMU_SPAPR_INFO_DDW	(1 << 0)	/* DDW supported */
+#define VFIO_IOMMU_SPAPR_INFO_DDW_START	(1 << 1)	/* DDW offset */
 	__u32 dma32_window_start;	/* 32 bit window start (bytes) */
 	__u32 dma32_window_size;	/* 32 bit window size (bytes) */
 	struct vfio_iommu_spapr_tce_ddw_info ddw;
+	__u64 dma64_window_start;
 };
 
 #define VFIO_IOMMU_SPAPR_TCE_GET_INFO	_IO(VFIO_TYPE, VFIO_BASE + 12)
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 750a0676e9b7..315fd56e51a7 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -691,7 +691,7 @@ static long tce_iommu_create_window(struct tce_container *container,
 	container->tables[num] = tbl;
 
 	/* Return start address assigned by platform in create_table() */
-	*start_addr = tbl->it_offset << tbl->it_page_shift;
+	*start_addr = (tbl->it_offset + tbl->it_tceoff) << tbl->it_page_shift;
 
 	return 0;
 
@@ -777,7 +777,7 @@ static long tce_iommu_ioctl(void *iommu_data,
 				 unsigned int cmd, unsigned long arg)
 {
 	struct tce_container *container = iommu_data;
-	unsigned long minsz, ddwsz;
+	unsigned long minsz;
 	long ret;
 
 	switch (cmd) {
@@ -842,12 +842,13 @@ static long tce_iommu_ioctl(void *iommu_data,
 			info.ddw.levels = table_group->max_levels;
 		}
 
-		ddwsz = offsetofend(struct vfio_iommu_spapr_tce_info, ddw);
+		info.flags |= VFIO_IOMMU_SPAPR_INFO_DDW_START;
+		info.dma64_window_start = table_group->tce64_start;
 
-		if (info.argsz >= ddwsz)
-			minsz = ddwsz;
+		if (info.argsz > sizeof(info))
+			info.argsz = sizeof(info);
 
-		if (copy_to_user((void __user *)arg, &info, minsz))
+		if (copy_to_user((void __user *)arg, &info, info.argsz))
 			return -EFAULT;
 
 		return 0;
-- 
2.17.1