env_dpdk: keep a memmap refcount of physical addresses

This allows us to avoid trying to map the same physical address to the
IOMMU in physical mode while still making sure that we don't
accidentally unmap that physical address before we are done referencing
it.

Change-Id: I947408411538b921bdc5a89ce8d5e40fd826e971
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/483133
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: SPDK CI Jenkins <sys_sgci@intel.com>

lib/env_dpdk/memory.c

@@ -778,14 +778,23 @@ static TAILQ_HEAD(, spdk_vtophys_pci_device) g_vtophys_pci_devices =
 	TAILQ_HEAD_INITIALIZER(g_vtophys_pci_devices);
 
 static struct spdk_mem_map *g_vtophys_map;
+static struct spdk_mem_map *g_phys_ref_map;
 
 #if SPDK_VFIO_ENABLED
 static int
 vtophys_iommu_map_dma(uint64_t vaddr, uint64_t iova, uint64_t size)
 {
 	struct spdk_vfio_dma_map *dma_map;
+	uint64_t refcount;
 	int ret;
 
+	refcount = spdk_mem_map_translate(g_phys_ref_map, iova, NULL);
+	assert(refcount < UINT64_MAX);
+	if (refcount > 0) {
+		spdk_mem_map_set_translation(g_phys_ref_map, iova, size, refcount + 1);
+		return 0;
+	}
+
 	dma_map = calloc(1, sizeof(*dma_map));
 	if (dma_map == NULL) {
 		return -ENOMEM;
@@ -832,13 +841,15 @@ vtophys_iommu_map_dma(uint64_t vaddr, uint64_t iova, uint64_t size)
 out_insert:
 	TAILQ_INSERT_TAIL(&g_vfio.maps, dma_map, tailq);
 	pthread_mutex_unlock(&g_vfio.mutex);
+	spdk_mem_map_set_translation(g_phys_ref_map, iova, size, refcount + 1);
 	return 0;
 }
 
 static int
 vtophys_iommu_unmap_dma(uint64_t iova, uint64_t size)
 {
 	struct spdk_vfio_dma_map *dma_map;
+	uint64_t refcount;
 	int ret;
 
 	pthread_mutex_lock(&g_vfio.mutex);
@@ -854,6 +865,18 @@ vtophys_iommu_unmap_dma(uint64_t iova, uint64_t size)
 		return -ENXIO;
 	}
 
+	refcount = spdk_mem_map_translate(g_phys_ref_map, iova, NULL);
+	assert(refcount < UINT64_MAX);
+	if (refcount > 0) {
+		spdk_mem_map_set_translation(g_phys_ref_map, iova, size, refcount - 1);
+	}
+
+	/* We still have outstanding references, don't clear it. */
+	if (refcount > 1) {
+		pthread_mutex_unlock(&g_vfio.mutex);
+		return 0;
+	}
+
 	/** don't support partial or multiple-page unmap for now */
 	assert(dma_map->map.size == size);
 
@@ -1383,10 +1406,21 @@ spdk_vtophys_init(void)
 		.are_contiguous = vtophys_check_contiguous_entries,
 	};
 
+	const struct spdk_mem_map_ops phys_ref_map_ops = {
+		.notify_cb = NULL,
+		.are_contiguous = NULL,
+	};
+
 #if SPDK_VFIO_ENABLED
 	spdk_vtophys_iommu_init();
 #endif
 
+	g_phys_ref_map = spdk_mem_map_alloc(0, &phys_ref_map_ops, NULL);
+	if (g_phys_ref_map == NULL) {
+		DEBUG_PRINT("phys_ref map allocation failed.\n");
+		return -ENOMEM;
+	}
+
 	g_vtophys_map = spdk_mem_map_alloc(SPDK_VTOPHYS_ERROR, &vtophys_map_ops, NULL);
 	if (g_vtophys_map == NULL) {
 		DEBUG_PRINT("vtophys map allocation failed\n");