[v4,1/1] vfio: modify spapr iommu support to use static window sizing
diff mbox series

Message ID 20201015172305.105717-2-drc@linux.vnet.ibm.com
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show
Series
  • vfio: change spapr DMA window sizing operation
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Commit Message

David Christensen Oct. 15, 2020, 5:23 p.m. UTC
The SPAPR IOMMU requires that a DMA window size be defined before memory
can be mapped for DMA. Current code dynamically modifies the DMA window
size in response to every new memory allocation which is potentially
dangerous because all existing mappings need to be unmapped/remapped in
order to resize the DMA window, leaving hardware holding IOVA addresses
that are temporarily unmapped.  The new SPAPR code statically assigns
the DMA window size on first use, using the largest physical memory
memory address when IOVA=PA and the highest existing memseg virtual
address when IOVA=VA.

Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
---
 lib/librte_eal/linux/eal_vfio.c | 412 +++++++++++++++-----------------
 1 file changed, 188 insertions(+), 224 deletions(-)

Comments

Thomas Monjalon Oct. 20, 2020, 12:05 p.m. UTC | #1
Anatoly, please could you review this patch?

15/10/2020 19:23, David Christensen:
> The SPAPR IOMMU requires that a DMA window size be defined before memory
> can be mapped for DMA. Current code dynamically modifies the DMA window
> size in response to every new memory allocation which is potentially
> dangerous because all existing mappings need to be unmapped/remapped in
> order to resize the DMA window, leaving hardware holding IOVA addresses
> that are temporarily unmapped.  The new SPAPR code statically assigns
> the DMA window size on first use, using the largest physical memory
> memory address when IOVA=PA and the highest existing memseg virtual
> address when IOVA=VA.
> 
> Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
Thomas Monjalon Oct. 29, 2020, 9:30 p.m. UTC | #2
Ping for review please

20/10/2020 14:05, Thomas Monjalon:
> Anatoly, please could you review this patch?
> 
> 15/10/2020 19:23, David Christensen:
> > The SPAPR IOMMU requires that a DMA window size be defined before memory
> > can be mapped for DMA. Current code dynamically modifies the DMA window
> > size in response to every new memory allocation which is potentially
> > dangerous because all existing mappings need to be unmapped/remapped in
> > order to resize the DMA window, leaving hardware holding IOVA addresses
> > that are temporarily unmapped.  The new SPAPR code statically assigns
> > the DMA window size on first use, using the largest physical memory
> > memory address when IOVA=PA and the highest existing memseg virtual
> > address when IOVA=VA.
> > 
> > Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
Burakov, Anatoly Nov. 2, 2020, 11:04 a.m. UTC | #3
On 15-Oct-20 6:23 PM, David Christensen wrote:
> The SPAPR IOMMU requires that a DMA window size be defined before memory
> can be mapped for DMA. Current code dynamically modifies the DMA window
> size in response to every new memory allocation which is potentially
> dangerous because all existing mappings need to be unmapped/remapped in
> order to resize the DMA window, leaving hardware holding IOVA addresses
> that are temporarily unmapped.  The new SPAPR code statically assigns
> the DMA window size on first use, using the largest physical memory
> memory address when IOVA=PA and the highest existing memseg virtual
> address when IOVA=VA.
> 
> Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
> ---

These changes are almost exclusively contained to PPC64 code, so with 
below changes,

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

> +static uint64_t
> +get_highest_mem_addr(struct spapr_size_walk_param *param)
> +{
> +	/* find the maximum IOVA address for setting the DMA window size */
> +	if (rte_eal_iova_mode() == RTE_IOVA_PA) {
> +		static const char proc_iomem[] = "/proc/iomem";
> +		static const char str_sysram[] = "System RAM";
> +		uint64_t start, end, max = 0;
> +		char *line = NULL;
> +		char *dash, *space;
> +		size_t line_len;
>   
> +		/*
> +		 * Example "System RAM" in /proc/iomem:
> +		 * 00000000-1fffffffff : System RAM
> +		 * 200000000000-201fffffffff : System RAM
> +		 */
> +		FILE *fd = fopen(proc_iomem, "r");
> +		if (fd == NULL) {
> +			RTE_LOG(ERR, EAL, "Cannot open %s\n", proc_iomem);
> +			return -1;
> +		}
> +		/* Scan /proc/iomem for the highest PA in the system */
> +		while (getline(&line, &line_len, fd) != -1) {
> +			if (strstr(line, str_sysram) == NULL)
> +				continue;
> +
> +			space = strstr(line, " ");
> +			dash = strstr(line, "-");
> +
> +			/* Validate the format of the memory string */
> +			if (space == NULL || dash == NULL || space < dash) {
> +				RTE_LOG(ERR, EAL, "Can't parse line \"%s\" in file %s\n",
> +					line, proc_iomem);
> +				continue;
> +			}
> +
> +			start = strtoull(line, NULL, 16);
> +			end   = strtoull(dash + 1, NULL, 16);
> +			RTE_LOG(DEBUG, EAL, "Found system RAM from 0x%" PRIx64
> +				" to 0x%" PRIx64 "\n", start, end);
> +			if (end > max)
> +				max = end;
> +		}
> +		free(line);
> +		fclose(fd);
> +
> +		if (max == 0) {
> +			RTE_LOG(ERR, EAL, "Failed to find valid \"System RAM\" "
> +				"entry in file %s\n", proc_iomem);
> +			return -1;
> +		}
> +
> +		return rte_align64pow2(max + 1);
> +	} else if (rte_eal_iova_mode() == RTE_IOVA_VA) {
> +		RTE_LOG(DEBUG, EAL, "Highest VA address in memseg list is 0x%"
> +			PRIx64 "\n", param->max_va);
> +		return rte_align64pow2(param->max_va);
> +	}
> +
> +	RTE_LOG(ERR, EAL, "Unsupported IOVA mode\n");
> +	return 0;

You're returning a uint64_t here, while also returning -1 in some of the 
error cases above, but not here. How about making the address an output 
parameter, and return 0 on success and -1 on error? It makes the code a 
bit messier at the call site, but would probably make more sense than 
returning 0 or -1 depending on which error condition you've hit.

Also, because of this, there's a bug below where you check for return 
value of 0, but not -1.

> +}
> +
> +
> +/*
> + * The SPAPRv2 IOMMU supports 2 DMA windows with starting
> + * address at 0 or 1<<59.  By default, a DMA window is set
> + * at address 0, 2GB long, with a 4KB page.  For DPDK we
> + * must remove the default window and setup a new DMA window
> + * based on the hugepage size and memory requirements of
> + * the application before we can map memory for DMA.
> + */
>   static int
> -vfio_spapr_window_size_walk(const struct rte_memseg_list *msl,
> -		const struct rte_memseg *ms, void *arg)
> +spapr_dma_win_size(void)
>   {
> -	struct spapr_walk_param *param = arg;
> -	uint64_t max = ms->iova + ms->len;
> -
> -	/* skip external memory that isn't a heap */
> -	if (msl->external && !msl->heap)
> -		return 0;
> +	struct spapr_size_walk_param param;
>   
> -	/* skip any segments with invalid IOVA addresses */
> -	if (ms->iova == RTE_BAD_IOVA)
> +	/* only create DMA window once */
> +	if (spapr_dma_win_len > 0)
>   		return 0;
>   
> -	if (max > param->window_size) {
> -		param->hugepage_sz = ms->hugepage_sz;
> -		param->window_size = max;
> +	/* walk the memseg list to find the page size/max VA address */
> +	memset(&param, 0, sizeof(param));
> +	if (rte_memseg_list_walk(vfio_spapr_size_walk, &param) < 0) {
> +		RTE_LOG(ERR, EAL, "Failed to walk memseg list for DMA window size\n");
> +		return -1;
>   	}
>   
> +	/* We can't be sure if DMA window covers external memory */
> +	if (param.is_user_managed)
> +		RTE_LOG(WARNING, EAL, "Detected user managed external memory which may not be managed by the IOMMU\n");
> +
> +	spapr_dma_win_len = get_highest_mem_addr(&param);
> +	if (spapr_dma_win_len == 0)
> +		return -1;

This error check doesn't catch all errors, as indicated above.

> +	RTE_LOG(DEBUG, EAL, "Setting DMA window size to 0x%" PRIx64 "\n",
> +		spapr_dma_win_len);
> +	spapr_dma_win_page_sz = param.page_sz;
> +	rte_mem_set_dma_mask(__builtin_ctzll(spapr_dma_win_len));
>   	return 0;
>   }
>   
>   static int
> -vfio_spapr_create_new_dma_window(int vfio_container_fd,
> -		struct vfio_iommu_spapr_tce_create *create) {
> +vfio_spapr_create_dma_window(int vfio_container_fd)
> +{
> +	struct vfio_iommu_spapr_tce_create create = {
> +		.argsz = sizeof(create), };
>   	struct vfio_iommu_spapr_tce_remove remove = {
> -		.argsz = sizeof(remove),
> -	};
> +		.argsz = sizeof(remove), };
>   	struct vfio_iommu_spapr_tce_info info = {
> -		.argsz = sizeof(info),
> -	};
> +		.argsz = sizeof(info), };
>   	int ret;
>   
> -	/* query spapr iommu info */
> +	ret = spapr_dma_win_size();
> +	if (ret < 0)
> +		return ret;
> +
>   	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_GET_INFO, &info);
>   	if (ret) {
> -		RTE_LOG(ERR, EAL, "  cannot get iommu info, "
> -				"error %i (%s)\n", errno, strerror(errno));
> +		RTE_LOG(ERR, EAL, "  can't get iommu info, error %i (%s)\n",
> +			errno, strerror(errno));
>   		return -1;
>   	}
>   
> -	/* remove default DMA of 32 bit window */
> +	/* remove default DMA window */
>   	remove.start_addr = info.dma32_window_start;
>   	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);

If you're never recreating a window, does it need to be removed? Or is 
this some kind of default window that is always present?

> -	if (ret) {
> -		RTE_LOG(ERR, EAL, "  cannot remove default DMA window, "
> -				"error %i (%s)\n", errno, strerror(errno));
> +	if (ret)
>   		return -1;
> -	}
>   
> -	/* create new DMA window */
> -	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_CREATE, create);
> +	/* create a new DMA window (start address is not selectable) */
> +	create.window_size = spapr_dma_win_len;
> +	create.page_shift  = __builtin_ctzll(spapr_dma_win_page_sz);
> +	create.levels = 1;
> +	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
>   	if (ret) {
> -#ifdef VFIO_IOMMU_SPAPR_INFO_DDW
> -		/* try possible page_shift and levels for workaround */
> +		/* if at first we don't succeed, try more levels */
>   		uint32_t levels;
>   
> -		for (levels = create->levels + 1;
> +		for (levels = create.levels + 1;
>   			ret && levels <= info.ddw.levels; levels++) {
> -			create->levels = levels;
> +			create.levels = levels;
>   			ret = ioctl(vfio_container_fd,
> -				VFIO_IOMMU_SPAPR_TCE_CREATE, create);
> -		}
> -#endif
> -		if (ret) {
> -			RTE_LOG(ERR, EAL, "  cannot create new DMA window, "
> -					"error %i (%s)\n", errno, strerror(errno));
> -			return -1;
> +				VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
>   		}
>   	}
> -
> -	if (create->start_addr != 0) {
> -		RTE_LOG(ERR, EAL, "  DMA window start address != 0\n");
> +	if (ret) {
> +		RTE_LOG(ERR, EAL, "  cannot create new DMA window, error %i (%s)\n",
> +			errno, strerror(errno));
> +		RTE_LOG(ERR, EAL, "  consider using a larger hugepage size "
> +			"if supported by the system\n");
>   		return -1;
>   	}
>   
> -	return 0;
> +	/* verify the start address  */
> +	if (create.start_addr != 0) {
> +		RTE_LOG(ERR, EAL, "  received unsupported start address 0x%"
> +			PRIx64 "\n", (uint64_t)create.start_addr);
> +		return -1;
> +	}
> +	return ret;
>   }
>   
>   static int
> -vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
> -		uint64_t len, int do_map)
> +vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr,
> +	uint64_t iova, uint64_t len, int do_map)

Nitpick, but this bit after newline should have two indents, not one.

Patch
diff mbox series

diff --git a/lib/librte_eal/linux/eal_vfio.c b/lib/librte_eal/linux/eal_vfio.c
index 380f2f44a..dfb1125f3 100644
--- a/lib/librte_eal/linux/eal_vfio.c
+++ b/lib/librte_eal/linux/eal_vfio.c
@@ -18,6 +18,7 @@ 
 #include "eal_memcfg.h"
 #include "eal_vfio.h"
 #include "eal_private.h"
+#include "eal_internal_cfg.h"
 
 #ifdef VFIO_PRESENT
 
@@ -536,17 +537,6 @@  vfio_mem_event_callback(enum rte_mem_event type, const void *addr, size_t len,
 		return;
 	}
 
-#ifdef RTE_ARCH_PPC_64
-	ms = rte_mem_virt2memseg(addr, msl);
-	while (cur_len < len) {
-		int idx = rte_fbarray_find_idx(&msl->memseg_arr, ms);
-
-		rte_fbarray_set_free(&msl->memseg_arr, idx);
-		cur_len += ms->len;
-		++ms;
-	}
-	cur_len = 0;
-#endif
 	/* memsegs are contiguous in memory */
 	ms = rte_mem_virt2memseg(addr, msl);
 
@@ -607,17 +597,6 @@  vfio_mem_event_callback(enum rte_mem_event type, const void *addr, size_t len,
 						iova_expected - iova_start, 0);
 		}
 	}
-#ifdef RTE_ARCH_PPC_64
-	cur_len = 0;
-	ms = rte_mem_virt2memseg(addr, msl);
-	while (cur_len < len) {
-		int idx = rte_fbarray_find_idx(&msl->memseg_arr, ms);
-
-		rte_fbarray_set_used(&msl->memseg_arr, idx);
-		cur_len += ms->len;
-		++ms;
-	}
-#endif
 }
 
 static int
@@ -1436,21 +1415,30 @@  vfio_type1_dma_map(int vfio_container_fd)
 	return rte_memseg_walk(type1_map, &vfio_container_fd);
 }
 
+/* Track the size of the statically allocated DMA window for SPAPR */
+uint64_t spapr_dma_win_len;
+uint64_t spapr_dma_win_page_sz;
+
 static int
 vfio_spapr_dma_do_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
 		uint64_t len, int do_map)
 {
-	struct vfio_iommu_type1_dma_map dma_map;
-	struct vfio_iommu_type1_dma_unmap dma_unmap;
-	int ret;
 	struct vfio_iommu_spapr_register_memory reg = {
 		.argsz = sizeof(reg),
+		.vaddr = (uintptr_t) vaddr,
+		.size = len,
 		.flags = 0
 	};
-	reg.vaddr = (uintptr_t) vaddr;
-	reg.size = len;
+	int ret;
 
 	if (do_map != 0) {
+		struct vfio_iommu_type1_dma_map dma_map;
+
+		if (iova + len > spapr_dma_win_len) {
+			RTE_LOG(ERR, EAL, "  dma map attempt outside DMA window\n");
+			return -1;
+		}
+
 		ret = ioctl(vfio_container_fd,
 				VFIO_IOMMU_SPAPR_REGISTER_MEMORY, &reg);
 		if (ret) {
@@ -1469,24 +1457,14 @@  vfio_spapr_dma_do_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
 
 		ret = ioctl(vfio_container_fd, VFIO_IOMMU_MAP_DMA, &dma_map);
 		if (ret) {
-			/**
-			 * In case the mapping was already done EBUSY will be
-			 * returned from kernel.
-			 */
-			if (errno == EBUSY) {
-				RTE_LOG(DEBUG, EAL,
-					" Memory segment is already mapped,"
-					" skipping");
-			} else {
-				RTE_LOG(ERR, EAL,
-					"  cannot set up DMA remapping,"
-					" error %i (%s)\n", errno,
-					strerror(errno));
-				return -1;
-			}
+			RTE_LOG(ERR, EAL, "  cannot map vaddr for IOMMU, error %i (%s)\n",
+				errno, strerror(errno));
+			return -1;
 		}
 
 	} else {
+		struct vfio_iommu_type1_dma_map dma_unmap;
+
 		memset(&dma_unmap, 0, sizeof(dma_unmap));
 		dma_unmap.argsz = sizeof(struct vfio_iommu_type1_dma_unmap);
 		dma_unmap.size = len;
@@ -1495,8 +1473,8 @@  vfio_spapr_dma_do_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
 		ret = ioctl(vfio_container_fd, VFIO_IOMMU_UNMAP_DMA,
 				&dma_unmap);
 		if (ret) {
-			RTE_LOG(ERR, EAL, "  cannot clear DMA remapping, error %i (%s)\n",
-					errno, strerror(errno));
+			RTE_LOG(ERR, EAL, "  cannot unmap vaddr for IOMMU, error %i (%s)\n",
+				errno, strerror(errno));
 			return -1;
 		}
 
@@ -1504,12 +1482,12 @@  vfio_spapr_dma_do_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
 				VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY, &reg);
 		if (ret) {
 			RTE_LOG(ERR, EAL, "  cannot unregister vaddr for IOMMU, error %i (%s)\n",
-					errno, strerror(errno));
+				errno, strerror(errno));
 			return -1;
 		}
 	}
 
-	return 0;
+	return ret;
 }
 
 static int
@@ -1526,251 +1504,237 @@  vfio_spapr_map_walk(const struct rte_memseg_list *msl,
 	if (ms->iova == RTE_BAD_IOVA)
 		return 0;
 
-	return vfio_spapr_dma_do_map(*vfio_container_fd, ms->addr_64, ms->iova,
-			ms->len, 1);
+	return vfio_spapr_dma_do_map(*vfio_container_fd,
+		ms->addr_64, ms->iova, ms->len, 1);
 }
 
+struct spapr_size_walk_param {
+	uint64_t max_va;
+	uint64_t page_sz;
+	bool is_user_managed;
+};
+
+/*
+ * In order to set the DMA window size required for the SPAPR IOMMU
+ * we need to walk the existing virtual memory allocations as well as
+ * find the hugepage size used.
+ */
 static int
-vfio_spapr_unmap_walk(const struct rte_memseg_list *msl,
-		const struct rte_memseg *ms, void *arg)
+vfio_spapr_size_walk(const struct rte_memseg_list *msl, void *arg)
 {
-	int *vfio_container_fd = arg;
+	struct spapr_size_walk_param *param = arg;
+	uint64_t max = (uint64_t) msl->base_va + (uint64_t) msl->len;
 
-	/* skip external memory that isn't a heap */
-	if (msl->external && !msl->heap)
+	if (msl->external && !msl->heap) {
+		/* ignore user managed external memory */
+		param->is_user_managed = true;
 		return 0;
+	}
 
-	/* skip any segments with invalid IOVA addresses */
-	if (ms->iova == RTE_BAD_IOVA)
-		return 0;
+	if (max > param->max_va) {
+		param->page_sz = msl->page_sz;
+		param->max_va = max;
+	}
 
-	return vfio_spapr_dma_do_map(*vfio_container_fd, ms->addr_64, ms->iova,
-			ms->len, 0);
+	return 0;
 }
 
-struct spapr_walk_param {
-	uint64_t window_size;
-	uint64_t hugepage_sz;
-};
+static uint64_t
+get_highest_mem_addr(struct spapr_size_walk_param *param)
+{
+	/* find the maximum IOVA address for setting the DMA window size */
+	if (rte_eal_iova_mode() == RTE_IOVA_PA) {
+		static const char proc_iomem[] = "/proc/iomem";
+		static const char str_sysram[] = "System RAM";
+		uint64_t start, end, max = 0;
+		char *line = NULL;
+		char *dash, *space;
+		size_t line_len;
 
+		/*
+		 * Example "System RAM" in /proc/iomem:
+		 * 00000000-1fffffffff : System RAM
+		 * 200000000000-201fffffffff : System RAM
+		 */
+		FILE *fd = fopen(proc_iomem, "r");
+		if (fd == NULL) {
+			RTE_LOG(ERR, EAL, "Cannot open %s\n", proc_iomem);
+			return -1;
+		}
+		/* Scan /proc/iomem for the highest PA in the system */
+		while (getline(&line, &line_len, fd) != -1) {
+			if (strstr(line, str_sysram) == NULL)
+				continue;
+
+			space = strstr(line, " ");
+			dash = strstr(line, "-");
+
+			/* Validate the format of the memory string */
+			if (space == NULL || dash == NULL || space < dash) {
+				RTE_LOG(ERR, EAL, "Can't parse line \"%s\" in file %s\n",
+					line, proc_iomem);
+				continue;
+			}
+
+			start = strtoull(line, NULL, 16);
+			end   = strtoull(dash + 1, NULL, 16);
+			RTE_LOG(DEBUG, EAL, "Found system RAM from 0x%" PRIx64
+				" to 0x%" PRIx64 "\n", start, end);
+			if (end > max)
+				max = end;
+		}
+		free(line);
+		fclose(fd);
+
+		if (max == 0) {
+			RTE_LOG(ERR, EAL, "Failed to find valid \"System RAM\" "
+				"entry in file %s\n", proc_iomem);
+			return -1;
+		}
+
+		return rte_align64pow2(max + 1);
+	} else if (rte_eal_iova_mode() == RTE_IOVA_VA) {
+		RTE_LOG(DEBUG, EAL, "Highest VA address in memseg list is 0x%"
+			PRIx64 "\n", param->max_va);
+		return rte_align64pow2(param->max_va);
+	}
+
+	RTE_LOG(ERR, EAL, "Unsupported IOVA mode\n");
+	return 0;
+}
+
+
+/*
+ * The SPAPRv2 IOMMU supports 2 DMA windows with starting
+ * address at 0 or 1<<59.  By default, a DMA window is set
+ * at address 0, 2GB long, with a 4KB page.  For DPDK we
+ * must remove the default window and setup a new DMA window
+ * based on the hugepage size and memory requirements of
+ * the application before we can map memory for DMA.
+ */
 static int
-vfio_spapr_window_size_walk(const struct rte_memseg_list *msl,
-		const struct rte_memseg *ms, void *arg)
+spapr_dma_win_size(void)
 {
-	struct spapr_walk_param *param = arg;
-	uint64_t max = ms->iova + ms->len;
-
-	/* skip external memory that isn't a heap */
-	if (msl->external && !msl->heap)
-		return 0;
+	struct spapr_size_walk_param param;
 
-	/* skip any segments with invalid IOVA addresses */
-	if (ms->iova == RTE_BAD_IOVA)
+	/* only create DMA window once */
+	if (spapr_dma_win_len > 0)
 		return 0;
 
-	if (max > param->window_size) {
-		param->hugepage_sz = ms->hugepage_sz;
-		param->window_size = max;
+	/* walk the memseg list to find the page size/max VA address */
+	memset(&param, 0, sizeof(param));
+	if (rte_memseg_list_walk(vfio_spapr_size_walk, &param) < 0) {
+		RTE_LOG(ERR, EAL, "Failed to walk memseg list for DMA window size\n");
+		return -1;
 	}
 
+	/* We can't be sure if DMA window covers external memory */
+	if (param.is_user_managed)
+		RTE_LOG(WARNING, EAL, "Detected user managed external memory which may not be managed by the IOMMU\n");
+
+	spapr_dma_win_len = get_highest_mem_addr(&param);
+	if (spapr_dma_win_len == 0)
+		return -1;
+	RTE_LOG(DEBUG, EAL, "Setting DMA window size to 0x%" PRIx64 "\n",
+		spapr_dma_win_len);
+	spapr_dma_win_page_sz = param.page_sz;
+	rte_mem_set_dma_mask(__builtin_ctzll(spapr_dma_win_len));
 	return 0;
 }
 
 static int
-vfio_spapr_create_new_dma_window(int vfio_container_fd,
-		struct vfio_iommu_spapr_tce_create *create) {
+vfio_spapr_create_dma_window(int vfio_container_fd)
+{
+	struct vfio_iommu_spapr_tce_create create = {
+		.argsz = sizeof(create), };
 	struct vfio_iommu_spapr_tce_remove remove = {
-		.argsz = sizeof(remove),
-	};
+		.argsz = sizeof(remove), };
 	struct vfio_iommu_spapr_tce_info info = {
-		.argsz = sizeof(info),
-	};
+		.argsz = sizeof(info), };
 	int ret;
 
-	/* query spapr iommu info */
+	ret = spapr_dma_win_size();
+	if (ret < 0)
+		return ret;
+
 	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_GET_INFO, &info);
 	if (ret) {
-		RTE_LOG(ERR, EAL, "  cannot get iommu info, "
-				"error %i (%s)\n", errno, strerror(errno));
+		RTE_LOG(ERR, EAL, "  can't get iommu info, error %i (%s)\n",
+			errno, strerror(errno));
 		return -1;
 	}
 
-	/* remove default DMA of 32 bit window */
+	/* remove default DMA window */
 	remove.start_addr = info.dma32_window_start;
 	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
-	if (ret) {
-		RTE_LOG(ERR, EAL, "  cannot remove default DMA window, "
-				"error %i (%s)\n", errno, strerror(errno));
+	if (ret)
 		return -1;
-	}
 
-	/* create new DMA window */
-	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_CREATE, create);
+	/* create a new DMA window (start address is not selectable) */
+	create.window_size = spapr_dma_win_len;
+	create.page_shift  = __builtin_ctzll(spapr_dma_win_page_sz);
+	create.levels = 1;
+	ret = ioctl(vfio_container_fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
 	if (ret) {
-#ifdef VFIO_IOMMU_SPAPR_INFO_DDW
-		/* try possible page_shift and levels for workaround */
+		/* if at first we don't succeed, try more levels */
 		uint32_t levels;
 
-		for (levels = create->levels + 1;
+		for (levels = create.levels + 1;
 			ret && levels <= info.ddw.levels; levels++) {
-			create->levels = levels;
+			create.levels = levels;
 			ret = ioctl(vfio_container_fd,
-				VFIO_IOMMU_SPAPR_TCE_CREATE, create);
-		}
-#endif
-		if (ret) {
-			RTE_LOG(ERR, EAL, "  cannot create new DMA window, "
-					"error %i (%s)\n", errno, strerror(errno));
-			return -1;
+				VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
 		}
 	}
-
-	if (create->start_addr != 0) {
-		RTE_LOG(ERR, EAL, "  DMA window start address != 0\n");
+	if (ret) {
+		RTE_LOG(ERR, EAL, "  cannot create new DMA window, error %i (%s)\n",
+			errno, strerror(errno));
+		RTE_LOG(ERR, EAL, "  consider using a larger hugepage size "
+			"if supported by the system\n");
 		return -1;
 	}
 
-	return 0;
+	/* verify the start address  */
+	if (create.start_addr != 0) {
+		RTE_LOG(ERR, EAL, "  received unsupported start address 0x%"
+			PRIx64 "\n", (uint64_t)create.start_addr);
+		return -1;
+	}
+	return ret;
 }
 
 static int
-vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
-		uint64_t len, int do_map)
+vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr,
+	uint64_t iova, uint64_t len, int do_map)
 {
-	struct spapr_walk_param param;
-	struct vfio_iommu_spapr_tce_create create = {
-		.argsz = sizeof(create),
-	};
-	struct vfio_config *vfio_cfg;
-	struct user_mem_maps *user_mem_maps;
-	int i, ret = 0;
-
-	vfio_cfg = get_vfio_cfg_by_container_fd(vfio_container_fd);
-	if (vfio_cfg == NULL) {
-		RTE_LOG(ERR, EAL, "  invalid container fd!\n");
-		return -1;
-	}
-
-	user_mem_maps = &vfio_cfg->mem_maps;
-	rte_spinlock_recursive_lock(&user_mem_maps->lock);
-
-	/* check if window size needs to be adjusted */
-	memset(&param, 0, sizeof(param));
-
-	/* we're inside a callback so use thread-unsafe version */
-	if (rte_memseg_walk_thread_unsafe(vfio_spapr_window_size_walk,
-				&param) < 0) {
-		RTE_LOG(ERR, EAL, "Could not get window size\n");
-		ret = -1;
-		goto out;
-	}
-
-	/* also check user maps */
-	for (i = 0; i < user_mem_maps->n_maps; i++) {
-		uint64_t max = user_mem_maps->maps[i].iova +
-				user_mem_maps->maps[i].len;
-		param.window_size = RTE_MAX(param.window_size, max);
-	}
-
-	/* sPAPR requires window size to be a power of 2 */
-	create.window_size = rte_align64pow2(param.window_size);
-	create.page_shift = __builtin_ctzll(param.hugepage_sz);
-	create.levels = 1;
+	int ret = 0;
 
 	if (do_map) {
-		/* re-create window and remap the entire memory */
-		if (iova + len > create.window_size) {
-			/* release all maps before recreating the window */
-			if (rte_memseg_walk_thread_unsafe(vfio_spapr_unmap_walk,
-					&vfio_container_fd) < 0) {
-				RTE_LOG(ERR, EAL, "Could not release DMA maps\n");
-				ret = -1;
-				goto out;
-			}
-			/* release all user maps */
-			for (i = 0; i < user_mem_maps->n_maps; i++) {
-				struct user_mem_map *map =
-						&user_mem_maps->maps[i];
-				if (vfio_spapr_dma_do_map(vfio_container_fd,
-						map->addr, map->iova, map->len,
-						0)) {
-					RTE_LOG(ERR, EAL, "Could not release user DMA maps\n");
-					ret = -1;
-					goto out;
-				}
-			}
-			create.window_size = rte_align64pow2(iova + len);
-			if (vfio_spapr_create_new_dma_window(vfio_container_fd,
-					&create) < 0) {
-				RTE_LOG(ERR, EAL, "Could not create new DMA window\n");
-				ret = -1;
-				goto out;
-			}
-			/* we're inside a callback, so use thread-unsafe version
-			 */
-			if (rte_memseg_walk_thread_unsafe(vfio_spapr_map_walk,
-					&vfio_container_fd) < 0) {
-				RTE_LOG(ERR, EAL, "Could not recreate DMA maps\n");
-				ret = -1;
-				goto out;
-			}
-			/* remap all user maps */
-			for (i = 0; i < user_mem_maps->n_maps; i++) {
-				struct user_mem_map *map =
-						&user_mem_maps->maps[i];
-				if (vfio_spapr_dma_do_map(vfio_container_fd,
-						map->addr, map->iova, map->len,
-						1)) {
-					RTE_LOG(ERR, EAL, "Could not recreate user DMA maps\n");
-					ret = -1;
-					goto out;
-				}
-			}
-		}
-		if (vfio_spapr_dma_do_map(vfio_container_fd, vaddr, iova, len, 1)) {
+		if (vfio_spapr_dma_do_map(vfio_container_fd,
+			vaddr, iova, len, 1)) {
 			RTE_LOG(ERR, EAL, "Failed to map DMA\n");
 			ret = -1;
-			goto out;
 		}
 	} else {
-		/* for unmap, check if iova within DMA window */
-		if (iova > create.window_size) {
-			RTE_LOG(ERR, EAL, "iova beyond DMA window for unmap");
+		if (vfio_spapr_dma_do_map(vfio_container_fd,
+			vaddr, iova, len, 0)) {
+			RTE_LOG(ERR, EAL, "Failed to unmap DMA\n");
 			ret = -1;
-			goto out;
 		}
-
-		vfio_spapr_dma_do_map(vfio_container_fd, vaddr, iova, len, 0);
 	}
-out:
-	rte_spinlock_recursive_unlock(&user_mem_maps->lock);
+
 	return ret;
 }
 
 static int
 vfio_spapr_dma_map(int vfio_container_fd)
 {
-	struct vfio_iommu_spapr_tce_create create = {
-		.argsz = sizeof(create),
-	};
-	struct spapr_walk_param param;
-
-	memset(&param, 0, sizeof(param));
-
-	/* create DMA window from 0 to max(phys_addr + len) */
-	rte_memseg_walk(vfio_spapr_window_size_walk, &param);
-
-	/* sPAPR requires window size to be a power of 2 */
-	create.window_size = rte_align64pow2(param.window_size);
-	create.page_shift = __builtin_ctzll(param.hugepage_sz);
-	create.levels = 1;
-
-	if (vfio_spapr_create_new_dma_window(vfio_container_fd, &create) < 0) {
-		RTE_LOG(ERR, EAL, "Could not create new DMA window\n");
+	if (vfio_spapr_create_dma_window(vfio_container_fd) < 0) {
+		RTE_LOG(ERR, EAL, "Could not create new DMA window!\n");
 		return -1;
 	}
 
-	/* map all DPDK segments for DMA. use 1:1 PA to IOVA mapping */
+	/* map all existing DPDK segments for DMA */
 	if (rte_memseg_walk(vfio_spapr_map_walk, &vfio_container_fd) < 0)
 		return -1;