memory: add way of checking iommu usage

Since the fuzz tester will be submitting random commands with random
memory addresses and such to the NVMe drives, we want to be especially
sure that we are using the IOMMU while running this test to prevent
memory corruption in the event that an errant command triggers a bad
DMA.
This function exposes to the application whether or not we are using the
IOMMU.

Change-Id: Ie4d26c706967a520967bfc81f72f7b581b792437
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/446568
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

include/spdk/env.h

@@ -573,6 +573,13 @@ size_t spdk_ring_enqueue(struct spdk_ring *ring, void **objs, size_t count);
  */
 size_t spdk_ring_dequeue(struct spdk_ring *ring, void **objs, size_t count);
 
+/**
+ * Reports whether the SPDK application is using the IOMMU for DMA
+ *
+ * \return True if we are using the IOMMU, false otherwise.
+ */
+bool spdk_iommu_is_enabled(void);
+
 #define SPDK_VTOPHYS_ERROR	(0xFFFFFFFFFFFFFFFFULL)
 
 /**

lib/env_dpdk/memory.c

@@ -779,6 +779,16 @@ spdk_mem_map_init(void)
 	return 0;
 }
 
+bool
+spdk_iommu_is_enabled(void)
+{
+#if SPDK_VFIO_ENABLED
+	return g_vfio.enabled && !g_vfio.noiommu_enabled;
+#else
+	return false;
+#endif
+}
+
 struct spdk_vtophys_pci_device {
 	struct rte_pci_device *pci_device;
 	TAILQ_ENTRY(spdk_vtophys_pci_device) tailq;