[dpdk-dev] [PATCH v3] eal/mem: preallocate VA space in no-huge mode

[Anatoly Burakov <anatoly.burakov@intel.com>]

When --no-huge mode is used, the memory is currently allocated with
mmap(NULL, ...). This is fine in most cases, but can fail in cases
where DPDK is run on a machine with an IOMMU that is of more limited
address width than that of a VA, because we're not specifying the
address hint for mmap() call.

Fix it by preallocating VA space before mapping it.

Cc: stable@dpdk.org

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---

Notes:
    v3:
    - Fix mmap flags used in place of offset
    - Fix using internal_config.memory in place of mem_sz
    - Add additional address sanity check
    
    v2:
    - Add unmap on unsuccessful mmap
    
    I couldn't figure out which specific commit has introduced
    the issue, so there's no fix tag. The most likely candidate
    is one that introduced the DMA mask thing in the first place
    but i'm not sure.

 lib/librte_eal/linux/eal/eal_memory.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/lib/librte_eal/linux/eal/eal_memory.c b/lib/librte_eal/linux/eal/eal_memory.c
index 5604c2a7c0..7a9c97ff88 100644
--- a/lib/librte_eal/linux/eal/eal_memory.c
+++ b/lib/librte_eal/linux/eal/eal_memory.c
@@ -1340,6 +1340,8 @@ eal_legacy_hugepage_init(void)
 
 	/* hugetlbfs can be disabled */
 	if (internal_config.no_hugetlbfs) {
+		void *prealloc_addr;
+		size_t mem_sz;
 		struct rte_memseg_list *msl;
 		int n_segs, cur_seg, fd, flags;
 #ifdef MEMFD_SUPPORTED
@@ -1395,17 +1397,31 @@ eal_legacy_hugepage_init(void)
 			}
 		}
 #endif
-		addr = mmap(NULL, internal_config.memory, PROT_READ | PROT_WRITE,
-				flags, fd, 0);
-		if (addr == MAP_FAILED) {
+		/* preallocate address space for the memory, so that it can be
+		 * fit into the DMA mask.
+		 */
+		mem_sz = internal_config.memory;
+		prealloc_addr = eal_get_virtual_area(
+				NULL, &mem_sz, page_sz, 0, 0);
+		if (prealloc_addr == NULL) {
+			RTE_LOG(ERR, EAL,
+					"%s: reserving memory area failed: "
+					"%s\n",
+					__func__, strerror(errno));
+			return -1;
+		}
+		addr = mmap(prealloc_addr, mem_sz, PROT_READ | PROT_WRITE,
+				flags | MAP_FIXED, fd, 0);
+		if (addr == MAP_FAILED || addr != prealloc_addr) {
 			RTE_LOG(ERR, EAL, "%s: mmap() failed: %s\n", __func__,
 					strerror(errno));
+			munmap(prealloc_addr, mem_sz);
 			return -1;
 		}
 		msl->base_va = addr;
 		msl->page_sz = page_sz;
 		msl->socket_id = 0;
-		msl->len = internal_config.memory;
+		msl->len = mem_sz;
 		msl->heap = 1;
 
 		/* we're in single-file segments mode, so only the segment list
-- 
2.17.1