[dpdk-dev] [PATCH] vfio: fix sPAPR IOMMU DMA window size

[Jonas Pfefferle]

DMA window size needs to be big enough to span all memory segment's
physical addresses. We do not need multiple levels of IOMMU tables
as we already span ~70TB of physical memory with 16MB hugepages.

Signed-off-by: Jonas Pfefferle <jpf at zurich.ibm.com>
---
 lib/librte_eal/linuxapp/eal/eal_vfio.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c b/lib/librte_eal/linuxapp/eal/eal_vfio.c
index 946df7e..8502216 100644
--- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
+++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
@@ -722,6 +722,18 @@ vfio_type1_dma_map(int vfio_container_fd)
 	return 0;
 }
 
+static uint64_t
+roundup_next_pow2(uint64_t n)
+{
+	uint32_t i;
+
+	n--;
+	for (i = 1; i < sizeof(n) * CHAR_BIT; i += i)
+		n |= n >> i;
+
+	return ++n;
+}
+
 static int
 vfio_spapr_dma_map(int vfio_container_fd)
 {
@@ -759,10 +771,12 @@ vfio_spapr_dma_map(int vfio_container_fd)
 		return -1;
 	}
 
-	/* calculate window size based on number of hugepages configured */
-	create.window_size = rte_eal_get_physmem_size();
+	/* physicaly pages are sorted descending i.e. ms[0].phys_addr is max */
+	/* create DMA window from 0 to max(phys_addr + len) */
+	/* sPAPR requires window size to be a power of 2 */
+	create.window_size = roundup_next_pow2(ms[0].phys_addr + ms[0].len);
 	create.page_shift = __builtin_ctzll(ms->hugepage_sz);
-	create.levels = 2;
+	create.levels = 1;
 
 	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
 	if (ret) {
@@ -771,6 +785,11 @@ vfio_spapr_dma_map(int vfio_container_fd)
 		return -1;
 	}
 
+	if (create.start_addr != 0) {
+		RTE_LOG(ERR, EAL, "  DMA window start address != 0\n");
+		return -1;
+	}
+
 	/* map all DPDK segments for DMA. use 1:1 PA to IOVA mapping */
 	for (i = 0; i < RTE_MAX_MEMSEG; i++) {
 		struct vfio_iommu_type1_dma_map dma_map;
-- 
2.7.4