[dpdk-dev] [PATCH 6/7] mem: add safe and unsafe versions for checking DMA mask

[Alejandro Lucero <alejandro.lucero@netronome.com>]

During memory initialization calling rte_mem_check_dma_mask
leads to a deadlock because memory_hotplug_lock is locked by a
writer, the current code in execution, and rte_memseg_walk
tries to lock as a reader.

This patch adds safe and unsafe versions for invoking the final
function specifying if the memory_hotplug_lock needs to be
acquired, this is for the safe version, or not, the unsafe one.
PMDs should use the safe version and just internal EAL memory
code should use the unsafe one.

Fixes: 223b7f1d5ef6 ("mem: add function for checking memseg IOVA")

Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
---
 drivers/net/nfp/nfp_net.c                  |  2 +-
 lib/librte_eal/common/eal_common_memory.c  | 24 +++++++++++++++---
 lib/librte_eal/common/include/rte_memory.h | 29 +++++++++++++++++++---
 lib/librte_eal/common/malloc_heap.c        |  2 +-
 lib/librte_eal/rte_eal_version.map         |  3 ++-
 5 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/drivers/net/nfp/nfp_net.c b/drivers/net/nfp/nfp_net.c
index 54c6da924..72c2d3cbb 100644
--- a/drivers/net/nfp/nfp_net.c
+++ b/drivers/net/nfp/nfp_net.c
@@ -2703,7 +2703,7 @@ nfp_net_init(struct rte_eth_dev *eth_dev)
 	pci_dev = RTE_ETH_DEV_TO_PCI(eth_dev);
 
 	/* NFP can not handle DMA addresses requiring more than 40 bits */
-	if (rte_mem_check_dma_mask(40)) {
+	if (rte_mem_check_dma_mask_safe(40)) {
 		RTE_LOG(ERR, PMD, "device %s can not be used:",
 				   pci_dev->device.name);
 		RTE_LOG(ERR, PMD, "\trestricted dma mask to 40 bits!\n");
diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 24b72fcb0..2eb3eb48a 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -446,11 +446,12 @@ check_iova(const struct rte_memseg_list *msl __rte_unused,
 #endif
 
 /* check memseg iovas are within the required range based on dma mask */
-int __rte_experimental
-rte_mem_check_dma_mask(uint8_t maskbits)
+static int __rte_experimental
+rte_mem_check_dma_mask(uint8_t maskbits, bool safe)
 {
 	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
 	uint64_t mask;
+	int ret;
 
 	/* sanity check */
 	if (maskbits > MAX_DMA_MASK_BITS) {
@@ -462,7 +463,12 @@ rte_mem_check_dma_mask(uint8_t maskbits)
 	/* create dma mask */
 	mask = ~((1ULL << maskbits) - 1);
 
-	if (rte_memseg_walk(check_iova, &mask))
+	if (safe)
+		ret = rte_memseg_walk(check_iova, &mask);
+	else
+		ret = rte_memseg_walk_thread_unsafe(check_iova, &mask);
+
+	if (ret)
 		/*
 		 * Dma mask precludes hugepage usage.
 		 * This device can not be used and we do not need to keep
@@ -480,6 +486,18 @@ rte_mem_check_dma_mask(uint8_t maskbits)
 	return 0;
 }
 
+int __rte_experimental
+rte_mem_check_dma_mask_safe(uint8_t maskbits)
+{
+	return rte_mem_check_dma_mask(maskbits, true);
+}
+
+int __rte_experimental
+rte_mem_check_dma_mask_unsafe(uint8_t maskbits)
+{
+	return rte_mem_check_dma_mask(maskbits, false);
+}
+
 /* set dma mask to use when memory initialization is done */
 void __rte_experimental
 rte_mem_set_dma_mask(uint8_t maskbits)
diff --git a/lib/librte_eal/common/include/rte_memory.h b/lib/librte_eal/common/include/rte_memory.h
index eff028db1..187a3c668 100644
--- a/lib/librte_eal/common/include/rte_memory.h
+++ b/lib/librte_eal/common/include/rte_memory.h
@@ -463,15 +463,38 @@ unsigned rte_memory_get_nchannel(void);
  */
 unsigned rte_memory_get_nrank(void);
 
-/* check memsegs iovas are within a range based on dma mask */
-int __rte_experimental rte_mem_check_dma_mask(uint8_t maskbits);
+/**
+ *  * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ *  Check memsegs iovas are within a range based on dma mask.
+ *
+ *  @param maskbits
+ *    Address width to check against.
+ */
+int __rte_experimental rte_mem_check_dma_mask_safe(uint8_t maskbits);
+
+/**
+ *  * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ *  Check memsegs iovas are within a range based on dma mask without acquiring
+ *  memory_hotplug_lock first.
+ *
+ *  This function is just for EAL core memory internal use. Drivers should
+ *  use the previous safe one.
+ *
+ *  @param maskbits
+ *    Address width to check against.
+ */
+int __rte_experimental rte_mem_check_dma_mask_unsafe(uint8_t maskbits);
 
 /**
  *  * @warning
  * @b EXPERIMENTAL: this API may change without prior notice
  *
  *  Set dma mask to use once memory initialization is done.
- *  Previous function rte_mem_check_dma_mask can not be used
+ *  Previous functions rte_mem_check_dma_mask_safe/unsafe can not be used
  *  safely until memory has been initialized.
  */
 void __rte_experimental rte_mem_set_dma_mask(uint8_t maskbits);
diff --git a/lib/librte_eal/common/malloc_heap.c b/lib/librte_eal/common/malloc_heap.c
index 711622f19..dd8b983e7 100644
--- a/lib/librte_eal/common/malloc_heap.c
+++ b/lib/librte_eal/common/malloc_heap.c
@@ -335,7 +335,7 @@ alloc_pages_on_heap(struct malloc_heap *heap, uint64_t pg_sz, size_t elt_size,
 	 * executed. For 2) implies the new memory can not be added.
 	 */
 	if (mcfg->dma_maskbits) {
-		if (rte_mem_check_dma_mask(mcfg->dma_maskbits)) {
+		if (rte_mem_check_dma_mask_unsafe(mcfg->dma_maskbits)) {
 			/* Currently this can only happen if IOMMU is enabled
 			 * with RTE_ARCH_X86. It is not safe to use this memory
 			 * so returning an error here.
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index ae24b5c73..f863903b6 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -296,7 +296,8 @@ EXPERIMENTAL {
 	rte_devargs_remove;
 	rte_devargs_type_count;
 	rte_mem_check_dma_mask;
-	rte_mem_set_dma_mask;
+	rte_mem_set_dma_mask_safe;
+	rte_mem_set_dma_mask_unsafe;
 	rte_eal_cleanup;
 	rte_fbarray_attach;
 	rte_fbarray_destroy;
-- 
2.17.1