[PATCH v9 0/5] Support add/remove memory region and get-max-slots

[PATCH v9 0/5] Support add/remove memory region and get-max-slots

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

This is version v9 of the patchset and it incorporates the
recommendations made by Stephen Hemminger.

Changes made to patch 3/5
- Restored max_guest_pages initial value to hardcoded 8 instead of
  VHOST_MEMORY_MAX_NREGIONS, matching upstream semantics.

Changes made to patch 4/5
- Added close(reg->fd) and reg->fd = -1 before goto close_msg_fds in the
  mmap failure path to fix fd leak after fd was moved from ctx->fds[0].
- Converted dev_invalidate_vrings from a plain function to a macro +
  implementation function pair, accepting message ID as a parameter so
  the static_assert reports the correct handler at each call site.
- Updated dev_invalidate_vrings call in add_mem_reg to pass
  VHOST_USER_ADD_MEM_REG as message ID.
- Updated dev_invalidate_vrings call in rem_mem_reg to pass
  VHOST_USER_ADD_MEM_REG as message ID.

This implementation has been extensively tested by doing Read/Write I/O
from multiple instances of fio + libblkio (front-end) talking to
spdk/dpdk (back-end) based drives. Tested with qemu front-end talking to
dpdk testpmd (back-end) performing add/removal of memory regions. Also
tested post-copy live migration after doing add_memory_region.

Version Log:
Version v9 (Current version): Incorporate code review suggestions from
Stephen Hemminger as described above.
Version v8:  Incorporate code review suggestions from Stephen Hemminger.
rewrite async_dma_map_region function to iterate guest pages by host
address range matching
change function dev_invalidate_vrings to accept a double pointer to
propagate pointer updates
new function remove_guest_pages was added
add_mem_reg error path was narrowed to only clean up the single failed
region instead of destroting all existing regions
Version v7: Incorporate code review suggestions from Maxime Coquelin.
Add debug messages to vhost_postcopy_register function.
Version v6: Added the enablement of this feature as a final patch in
this patch-set and other code optimizations as suggested by Maxime
Coquelin.
Version v5: removed the patch that increased the number of memory regions
from 8 to 128. This will be submitted as a separate feature at a later
point after incorporating additional optimizations. Also includes code
optimizations as suggested by Feng Cheng Wen.
Version v4: code optimizations as suggested by Feng Cheng Wen.
Version v3: code optimizations as suggested by Maxime Coquelin
and Thomas Monjalon.
Version v2: code optimizations as suggested by Maxime Coquelin.
Version v1: Initial patch set.

Pravin M Bathija (5):
  vhost: add user to mailmap and define to vhost hdr
  vhost_user: header defines for add/rem mem region
  vhost_user: support function defines for back-end
  vhost_user: Function defs for add/rem mem regions
  vhost_user: enable configure memory slots

 .mailmap               |   1 +
 lib/vhost/rte_vhost.h  |   4 +
 lib/vhost/vhost_user.c | 403 ++++++++++++++++++++++++++++++++++++-----
 lib/vhost/vhost_user.h |  10 +
 4 files changed, 375 insertions(+), 43 deletions(-)

-- 
2.43.0

[PATCH v9 1/5] vhost: add user to mailmap and define to vhost hdr

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

- add user to mailmap file.
- define a bit-field called VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS
  that depicts if the feature/capability to add/remove memory regions
  is supported. This is a part of the overall support for add/remove
  memory region feature in this patchset.

Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
---
 .mailmap              | 1 +
 lib/vhost/rte_vhost.h | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/.mailmap b/.mailmap
index 0e0d83e1c6..cc44e27036 100644
--- a/.mailmap
+++ b/.mailmap
@@ -1295,6 +1295,7 @@ Prateek Agarwal <prateekag@cse.iitb.ac.in>
 Prathisna Padmasanan <prathisna.padmasanan@intel.com>
 Praveen Kaligineedi <pkaligineedi@google.com>
 Praveen Shetty <praveen.shetty@intel.com>
+Pravin M Bathija <pravin.bathija@dell.com>
 Pravin Pathak <pravin.pathak.dev@gmail.com> <pravin.pathak@intel.com>
 Prince Takkar <ptakkar@marvell.com>
 Priyalee Kushwaha <priyalee.kushwaha@intel.com>
diff --git a/lib/vhost/rte_vhost.h b/lib/vhost/rte_vhost.h
index 2f7c4c0080..a7f9700538 100644
--- a/lib/vhost/rte_vhost.h
+++ b/lib/vhost/rte_vhost.h
@@ -109,6 +109,10 @@ extern "C" {
 #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
 #endif
 
+#ifndef VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS
+#define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15
+#endif
+
 #ifndef VHOST_USER_PROTOCOL_F_STATUS
 #define VHOST_USER_PROTOCOL_F_STATUS 16
 #endif
-- 
2.43.0

[PATCH v9 2/5] vhost_user: header defines for add/rem mem region

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

The changes in this file cover the enum message requests for
supporting add/remove memory regions. The front-end vhost-user
client sends messages like get max memory slots, add memory region
and remove memory region which are covered in these changes which
are on the vhost-user back-end. The changes also include data structure
definition of memory region to be added/removed. The data structure
VhostUserMsg has been changed to include the memory region.

Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
---
 lib/vhost/vhost_user.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/vhost/vhost_user.h b/lib/vhost/vhost_user.h
index ef486545ba..f8d921f7f1 100644
--- a/lib/vhost/vhost_user.h
+++ b/lib/vhost/vhost_user.h
@@ -67,6 +67,9 @@ typedef enum VhostUserRequest {
 	VHOST_USER_POSTCOPY_END = 30,
 	VHOST_USER_GET_INFLIGHT_FD = 31,
 	VHOST_USER_SET_INFLIGHT_FD = 32,
+	VHOST_USER_GET_MAX_MEM_SLOTS = 36,
+	VHOST_USER_ADD_MEM_REG = 37,
+	VHOST_USER_REM_MEM_REG = 38,
 	VHOST_USER_SET_STATUS = 39,
 	VHOST_USER_GET_STATUS = 40,
 } VhostUserRequest;
@@ -91,6 +94,11 @@ typedef struct VhostUserMemory {
 	VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
 } VhostUserMemory;
 
+typedef struct VhostUserSingleMemReg {
+	uint64_t padding;
+	VhostUserMemoryRegion region;
+} VhostUserSingleMemReg;
+
 typedef struct VhostUserLog {
 	uint64_t mmap_size;
 	uint64_t mmap_offset;
@@ -186,6 +194,7 @@ typedef struct __rte_packed_begin VhostUserMsg {
 		struct vhost_vring_state state;
 		struct vhost_vring_addr addr;
 		VhostUserMemory memory;
+		VhostUserSingleMemReg memory_single;
 		VhostUserLog    log;
 		struct vhost_iotlb_msg iotlb;
 		VhostUserCryptoSessionParam crypto_session;
-- 
2.43.0

[PATCH v9 3/5] vhost_user: support function defines for back-end

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

Here we define support functions which are called from the various
vhost-user back-end message functions like set memory table, get
memory slots, add memory region, remove memory region.  These are
essentially common functions to initialize memory, unmap a set of
memory regions, perform register copy, align memory addresses,
dma map/unmap a single memory region and remove guest pages by
removing all entries belonging to a given memory region.

Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
---
 lib/vhost/vhost_user.c | 146 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 136 insertions(+), 10 deletions(-)

diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 4bfb13fb98..1f96ecf963 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -171,6 +171,52 @@ get_blk_size(int fd)
 	return ret == -1 ? (uint64_t)-1 : (uint64_t)stat.st_blksize;
 }
 
+static int
+async_dma_map_region(struct virtio_net *dev, struct rte_vhost_mem_region *reg, bool do_map)
+{
+	uint32_t i;
+	int ret;
+	uint64_t reg_start = reg->host_user_addr;
+	uint64_t reg_end = reg_start + reg->size;
+
+	for (i = 0; i < dev->nr_guest_pages; i++) {
+		struct guest_page *page = &dev->guest_pages[i];
+
+		/* Only process pages belonging to this region */
+		if (page->host_user_addr < reg_start ||
+		    page->host_user_addr >= reg_end)
+			continue;
+
+		if (do_map) {
+			ret = rte_vfio_container_dma_map(RTE_VFIO_DEFAULT_CONTAINER_FD,
+					page->host_user_addr,
+					page->host_iova,
+					page->size);
+			if (ret) {
+				if (rte_errno == ENODEV)
+					return 0;
+
+				VHOST_CONFIG_LOG(dev->ifname, ERR, "DMA engine map failed");
+				return -1;
+			}
+		} else {
+			ret = rte_vfio_container_dma_unmap(RTE_VFIO_DEFAULT_CONTAINER_FD,
+					page->host_user_addr,
+					page->host_iova,
+					page->size);
+			if (ret) {
+				if (rte_errno == EINVAL)
+					return 0;
+
+				VHOST_CONFIG_LOG(dev->ifname, ERR, "DMA engine unmap failed");
+				return -1;
+			}
+		}
+	}
+
+	return 0;
+}
+
 static void
 async_dma_map(struct virtio_net *dev, bool do_map)
 {
@@ -225,7 +271,17 @@ async_dma_map(struct virtio_net *dev, bool do_map)
 }
 
 static void
-free_mem_region(struct virtio_net *dev)
+free_mem_region(struct rte_vhost_mem_region *reg)
+{
+	if (reg != NULL && reg->mmap_addr) {
+		munmap(reg->mmap_addr, reg->mmap_size);
+		close(reg->fd);
+		memset(reg, 0, sizeof(struct rte_vhost_mem_region));
+	}
+}
+
+static void
+free_all_mem_regions(struct virtio_net *dev)
 {
 	uint32_t i;
 	struct rte_vhost_mem_region *reg;
@@ -236,12 +292,10 @@ free_mem_region(struct virtio_net *dev)
 	if (dev->async_copy && rte_vfio_is_enabled("vfio"))
 		async_dma_map(dev, false);
 
-	for (i = 0; i < dev->mem->nregions; i++) {
+	for (i = 0; i < VHOST_MEMORY_MAX_NREGIONS; i++) {
 		reg = &dev->mem->regions[i];
-		if (reg->host_user_addr) {
-			munmap(reg->mmap_addr, reg->mmap_size);
-			close(reg->fd);
-		}
+		if (reg->mmap_addr)
+			free_mem_region(reg);
 	}
 }
 
@@ -255,7 +309,7 @@ vhost_backend_cleanup(struct virtio_net *dev)
 		vdpa_dev->ops->dev_cleanup(dev->vid);
 
 	if (dev->mem) {
-		free_mem_region(dev);
+		free_all_mem_regions(dev);
 		rte_free(dev->mem);
 		dev->mem = NULL;
 	}
@@ -704,7 +758,7 @@ numa_realloc(struct virtio_net **pdev, struct vhost_virtqueue **pvq)
 	vhost_devices[dev->vid] = dev;
 
 	mem_size = sizeof(struct rte_vhost_memory) +
-		sizeof(struct rte_vhost_mem_region) * dev->mem->nregions;
+		sizeof(struct rte_vhost_mem_region) * VHOST_MEMORY_MAX_NREGIONS;
 	mem = rte_realloc_socket(dev->mem, mem_size, 0, node);
 	if (!mem) {
 		VHOST_CONFIG_LOG(dev->ifname, ERR,
@@ -808,8 +862,10 @@ hua_to_alignment(struct rte_vhost_memory *mem, void *ptr)
 	uint32_t i;
 	uintptr_t hua = (uintptr_t)ptr;
 
-	for (i = 0; i < mem->nregions; i++) {
+	for (i = 0; i < VHOST_MEMORY_MAX_NREGIONS; i++) {
 		r = &mem->regions[i];
+		if (r->host_user_addr == 0)
+			continue;
 		if (hua >= r->host_user_addr &&
 			hua < r->host_user_addr + r->size) {
 			return get_blk_size(r->fd);
@@ -1136,6 +1192,24 @@ add_guest_pages(struct virtio_net *dev, struct rte_vhost_mem_region *reg,
 	return 0;
 }
 
+static void
+remove_guest_pages(struct virtio_net *dev, struct rte_vhost_mem_region *reg)
+{
+	uint64_t reg_start = reg->host_user_addr;
+	uint64_t reg_end = reg_start + reg->size;
+	uint32_t i, j = 0;
+
+	for (i = 0; i < dev->nr_guest_pages; i++) {
+		if (dev->guest_pages[i].host_user_addr >= reg_start &&
+		    dev->guest_pages[i].host_user_addr < reg_end)
+			continue;
+		if (j != i)
+			dev->guest_pages[j] = dev->guest_pages[i];
+		j++;
+	}
+	dev->nr_guest_pages = j;
+}
+
 #ifdef RTE_LIBRTE_VHOST_DEBUG
 /* TODO: enable it only in debug mode? */
 static void
@@ -1246,10 +1320,14 @@ vhost_user_postcopy_register(struct virtio_net *dev, int main_fd,
 	 * DPDK's virtual address with Qemu, so that Qemu can
 	 * retrieve the region offset when handling userfaults.
 	 */
+	int reg_msg_index = 0;
 	memory = &ctx->msg.payload.memory;
 	for (i = 0; i < memory->nregions; i++) {
 		reg = &dev->mem->regions[i];
-		memory->regions[i].userspace_addr = reg->host_user_addr;
+		if (reg->host_user_addr == 0)
+			continue;
+		memory->regions[reg_msg_index].userspace_addr = reg->host_user_addr;
+		reg_msg_index++;
 	}
 
 	/* Send the addresses back to qemu */
@@ -1278,6 +1356,8 @@ vhost_user_postcopy_register(struct virtio_net *dev, int main_fd,
 	/* Now userfault register and we can use the memory */
 	for (i = 0; i < memory->nregions; i++) {
 		reg = &dev->mem->regions[i];
+		if (reg->host_user_addr == 0)
+			continue;
 		if (vhost_user_postcopy_region_register(dev, reg) < 0)
 			return -1;
 	}
@@ -1382,6 +1462,52 @@ vhost_user_mmap_region(struct virtio_net *dev,
 	return 0;
 }
 
+static int
+vhost_user_initialize_memory(struct virtio_net **pdev)
+{
+	struct virtio_net *dev = *pdev;
+	int numa_node = SOCKET_ID_ANY;
+
+	if (dev->mem != NULL) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR,
+			"memory already initialized, free it first");
+		return -1;
+	}
+
+	/*
+	 * If VQ 0 has already been allocated, try to allocate on the same
+	 * NUMA node. It can be reallocated later in numa_realloc().
+	 */
+	if (dev->nr_vring > 0)
+		numa_node = dev->virtqueue[0]->numa_node;
+
+	dev->nr_guest_pages = 0;
+	if (dev->guest_pages == NULL) {
+		dev->max_guest_pages = 8;
+		dev->guest_pages = rte_zmalloc_socket(NULL,
+					dev->max_guest_pages *
+					sizeof(struct guest_page),
+					RTE_CACHE_LINE_SIZE,
+					numa_node);
+		if (dev->guest_pages == NULL) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"failed to allocate memory for dev->guest_pages");
+			return -1;
+		}
+	}
+
+	dev->mem = rte_zmalloc_socket("vhost-mem-table", sizeof(struct rte_vhost_memory) +
+		sizeof(struct rte_vhost_mem_region) * VHOST_MEMORY_MAX_NREGIONS, 0, numa_node);
+	if (dev->mem == NULL) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR, "failed to allocate memory for dev->mem");
+		rte_free(dev->guest_pages);
+		dev->guest_pages = NULL;
+		return -1;
+	}
+
+	return 0;
+}
+
 static int
 vhost_user_set_mem_table(struct virtio_net **pdev,
 			struct vhu_msg_context *ctx,
-- 
2.43.0

[PATCH v9 4/5] vhost_user: Function defs for add/rem mem regions

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

These changes cover the function definition for add/remove memory
region calls which are invoked on receiving vhost user message from
vhost user front-end (e.g. Qemu). In our case, in addition to testing
with qemu front-end, the testing has also been performed with libblkio
front-end and spdk/dpdk back-end. We did I/O using libblkio based device
driver, to spdk based drives. There are also changes for set_mem_table
and new definition for get memory slots. Our changes optimize the set
memory table call to use common support functions. Message get memory
slots is how the vhost-user front-end queries the vhost-user back-end
about the number of memory slots available to be registered by the
back-end. In addition support function to invalidate vring is also
defined which is used in add/remove memory region functions.

Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
---
 lib/vhost/vhost_user.c | 257 +++++++++++++++++++++++++++++++++++------
 1 file changed, 224 insertions(+), 33 deletions(-)

diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 1f96ecf963..a296adde39 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -71,6 +71,9 @@ VHOST_MESSAGE_HANDLER(VHOST_USER_SET_FEATURES, vhost_user_set_features, false, t
 VHOST_MESSAGE_HANDLER(VHOST_USER_SET_OWNER, vhost_user_set_owner, false, true) \
 VHOST_MESSAGE_HANDLER(VHOST_USER_RESET_OWNER, vhost_user_reset_owner, false, false) \
 VHOST_MESSAGE_HANDLER(VHOST_USER_SET_MEM_TABLE, vhost_user_set_mem_table, true, true) \
+VHOST_MESSAGE_HANDLER(VHOST_USER_GET_MAX_MEM_SLOTS, vhost_user_get_max_mem_slots, false, false) \
+VHOST_MESSAGE_HANDLER(VHOST_USER_ADD_MEM_REG, vhost_user_add_mem_reg, true, true) \
+VHOST_MESSAGE_HANDLER(VHOST_USER_REM_MEM_REG, vhost_user_rem_mem_reg, true, true) \
 VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_BASE, vhost_user_set_log_base, true, true) \
 VHOST_MESSAGE_HANDLER(VHOST_USER_SET_LOG_FD, vhost_user_set_log_fd, true, true) \
 VHOST_MESSAGE_HANDLER(VHOST_USER_SET_VRING_NUM, vhost_user_set_vring_num, false, true) \
@@ -1516,7 +1519,6 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
 	struct virtio_net *dev = *pdev;
 	struct VhostUserMemory *memory = &ctx->msg.payload.memory;
 	struct rte_vhost_mem_region *reg;
-	int numa_node = SOCKET_ID_ANY;
 	uint64_t mmap_offset;
 	uint32_t i;
 	bool async_notify = false;
@@ -1561,39 +1563,13 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
 		if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
 			vhost_user_iotlb_flush_all(dev);
 
-		free_mem_region(dev);
+		free_all_mem_regions(dev);
 		rte_free(dev->mem);
 		dev->mem = NULL;
 	}
 
-	/*
-	 * If VQ 0 has already been allocated, try to allocate on the same
-	 * NUMA node. It can be reallocated later in numa_realloc().
-	 */
-	if (dev->nr_vring > 0)
-		numa_node = dev->virtqueue[0]->numa_node;
-
-	dev->nr_guest_pages = 0;
-	if (dev->guest_pages == NULL) {
-		dev->max_guest_pages = 8;
-		dev->guest_pages = rte_zmalloc_socket(NULL,
-					dev->max_guest_pages *
-					sizeof(struct guest_page),
-					RTE_CACHE_LINE_SIZE,
-					numa_node);
-		if (dev->guest_pages == NULL) {
-			VHOST_CONFIG_LOG(dev->ifname, ERR,
-				"failed to allocate memory for dev->guest_pages");
-			goto close_msg_fds;
-		}
-	}
-
-	dev->mem = rte_zmalloc_socket("vhost-mem-table", sizeof(struct rte_vhost_memory) +
-		sizeof(struct rte_vhost_mem_region) * memory->nregions, 0, numa_node);
-	if (dev->mem == NULL) {
-		VHOST_CONFIG_LOG(dev->ifname, ERR, "failed to allocate memory for dev->mem");
-		goto free_guest_pages;
-	}
+	if (vhost_user_initialize_memory(pdev) < 0)
+		goto close_msg_fds;
 
 	for (i = 0; i < memory->nregions; i++) {
 		reg = &dev->mem->regions[i];
@@ -1657,11 +1633,9 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
 	return RTE_VHOST_MSG_RESULT_OK;
 
 free_mem_table:
-	free_mem_region(dev);
+	free_all_mem_regions(dev);
 	rte_free(dev->mem);
 	dev->mem = NULL;
-
-free_guest_pages:
 	rte_free(dev->guest_pages);
 	dev->guest_pages = NULL;
 close_msg_fds:
@@ -1669,6 +1643,223 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
 	return RTE_VHOST_MSG_RESULT_ERR;
 }
 
+
+static int
+vhost_user_get_max_mem_slots(struct virtio_net **pdev __rte_unused,
+			struct vhu_msg_context *ctx,
+			int main_fd __rte_unused)
+{
+	uint32_t max_mem_slots = VHOST_MEMORY_MAX_NREGIONS;
+
+	ctx->msg.payload.u64 = (uint64_t)max_mem_slots;
+	ctx->msg.size = sizeof(ctx->msg.payload.u64);
+	ctx->fd_num = 0;
+
+	return RTE_VHOST_MSG_RESULT_REPLY;
+}
+
+static void
+_dev_invalidate_vrings(struct virtio_net **pdev)
+{
+	struct virtio_net *dev = *pdev;
+	uint32_t i;
+
+	for (i = 0; i < dev->nr_vring; i++) {
+		struct vhost_virtqueue *vq = dev->virtqueue[i];
+
+		if (!vq)
+			continue;
+
+		if (vq->desc || vq->avail || vq->used) {
+			vq_assert_lock(dev, vq);
+
+			/*
+			 * If the memory table got updated, the ring addresses
+			 * need to be translated again as virtual addresses have
+			 * changed.
+			 */
+			vring_invalidate(dev, vq);
+
+			translate_ring_addresses(&dev, &vq);
+		}
+	}
+
+	*pdev = dev;
+}
+
+/*
+ * Macro wrapper that performs the compile-time lock assertion with the
+ * correct message ID at the call site, then calls the implementation.
+ */
+#define dev_invalidate_vrings(pdev, id) do { \
+	static_assert(id ## _LOCK_ALL_QPS, \
+		#id " handler is not declared as locking all queue pairs"); \
+	_dev_invalidate_vrings(pdev); \
+} while (0)
+
+static int
+vhost_user_add_mem_reg(struct virtio_net **pdev,
+			struct vhu_msg_context *ctx,
+			int main_fd __rte_unused)
+{
+	uint32_t i;
+	struct virtio_net *dev = *pdev;
+	struct VhostUserMemoryRegion *region = &ctx->msg.payload.memory_single.region;
+
+	/* convert first region add to normal memory table set */
+	if (dev->mem == NULL) {
+		if (vhost_user_initialize_memory(pdev) < 0)
+			goto close_msg_fds;
+	}
+
+	/* make sure new region will fit */
+	if (dev->mem->nregions >= VHOST_MEMORY_MAX_NREGIONS) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR, "too many memory regions already (%u)",
+									dev->mem->nregions);
+		goto close_msg_fds;
+	}
+
+	/* make sure supplied memory fd present */
+	if (ctx->fd_num != 1) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR, "fd count makes no sense (%u)", ctx->fd_num);
+		goto close_msg_fds;
+	}
+
+	/* Make sure no overlap in guest virtual address space */
+	for (i = 0; i < dev->mem->nregions; i++) {
+		struct rte_vhost_mem_region *current_region = &dev->mem->regions[i];
+		uint64_t current_region_guest_start = current_region->guest_user_addr;
+		uint64_t current_region_guest_end = current_region_guest_start
+							+ current_region->size - 1;
+		uint64_t proposed_region_guest_start = region->userspace_addr;
+		uint64_t proposed_region_guest_end = proposed_region_guest_start
+							+ region->memory_size - 1;
+
+		if (!((proposed_region_guest_end < current_region_guest_start) ||
+			(proposed_region_guest_start > current_region_guest_end))) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"requested memory region overlaps with another region");
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"\tRequested region address:0x%" PRIx64,
+				region->userspace_addr);
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"\tRequested region size:0x%" PRIx64,
+				region->memory_size);
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"\tOverlapping region address:0x%" PRIx64,
+				current_region->guest_user_addr);
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"\tOverlapping region size:0x%" PRIx64,
+				current_region->size);
+			goto close_msg_fds;
+		}
+	}
+
+	/* New region goes at the end of the contiguous array */
+	struct rte_vhost_mem_region *reg = &dev->mem->regions[dev->mem->nregions];
+
+	reg->guest_phys_addr = region->guest_phys_addr;
+	reg->guest_user_addr = region->userspace_addr;
+	reg->size            = region->memory_size;
+	reg->fd              = ctx->fds[0];
+	ctx->fds[0]          = -1;
+
+	if (vhost_user_mmap_region(dev, reg, region->mmap_offset) < 0) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR, "failed to mmap region");
+		close(reg->fd);
+		reg->fd = -1;
+		goto close_msg_fds;
+	}
+
+	dev->mem->nregions++;
+
+	if (dev->async_copy && rte_vfio_is_enabled("vfio")) {
+		if (async_dma_map_region(dev, reg, true) < 0)
+			goto free_new_region;
+	}
+
+	if (dev->postcopy_listening) {
+		/*
+		 * Cannot use vhost_user_postcopy_register() here because it
+		 * reads ctx->msg.payload.memory (SET_MEM_TABLE layout), but
+		 * ADD_MEM_REG uses the memory_single payload.  Register the
+		 * single new region directly instead.
+		 */
+		if (vhost_user_postcopy_region_register(dev, reg) < 0)
+			goto free_new_region;
+	}
+
+	dev_invalidate_vrings(pdev, VHOST_USER_ADD_MEM_REG);
+	dev = *pdev;
+	dump_guest_pages(dev);
+
+	return RTE_VHOST_MSG_RESULT_OK;
+
+free_new_region:
+	if (dev->async_copy && rte_vfio_is_enabled("vfio"))
+		async_dma_map_region(dev, reg, false);
+	remove_guest_pages(dev, reg);
+	free_mem_region(reg);
+	dev->mem->nregions--;
+close_msg_fds:
+	close_msg_fds(ctx);
+	return RTE_VHOST_MSG_RESULT_ERR;
+}
+
+static int
+vhost_user_rem_mem_reg(struct virtio_net **pdev,
+			struct vhu_msg_context *ctx,
+			int main_fd __rte_unused)
+{
+	uint32_t i;
+	struct virtio_net *dev = *pdev;
+	struct VhostUserMemoryRegion *region = &ctx->msg.payload.memory_single.region;
+
+	if (dev->mem == NULL || dev->mem->nregions == 0) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR, "no memory regions to remove");
+		close_msg_fds(ctx);
+		return RTE_VHOST_MSG_RESULT_ERR;
+	}
+
+	for (i = 0; i < dev->mem->nregions; i++) {
+		struct rte_vhost_mem_region *current_region = &dev->mem->regions[i];
+
+		/*
+		 * According to the vhost-user specification:
+		 * The memory region to be removed is identified by its GPA,
+		 * user address and size. The mmap offset is ignored.
+		 */
+		if (region->userspace_addr == current_region->guest_user_addr
+			&& region->guest_phys_addr == current_region->guest_phys_addr
+			&& region->memory_size == current_region->size) {
+			if (dev->async_copy && rte_vfio_is_enabled("vfio"))
+				async_dma_map_region(dev, current_region, false);
+			remove_guest_pages(dev, current_region);
+			dev_invalidate_vrings(pdev, VHOST_USER_REM_MEM_REG);
+			dev = *pdev;
+			free_mem_region(current_region);
+
+			/* Compact the regions array to keep it contiguous */
+			if (i < dev->mem->nregions - 1) {
+				memmove(&dev->mem->regions[i],
+					&dev->mem->regions[i + 1],
+					(dev->mem->nregions - 1 - i) *
+					sizeof(struct rte_vhost_mem_region));
+				memset(&dev->mem->regions[dev->mem->nregions - 1],
+					0, sizeof(struct rte_vhost_mem_region));
+			}
+
+			dev->mem->nregions--;
+			close_msg_fds(ctx);
+			return RTE_VHOST_MSG_RESULT_OK;
+		}
+	}
+
+	VHOST_CONFIG_LOG(dev->ifname, ERR, "failed to find region");
+	close_msg_fds(ctx);
+	return RTE_VHOST_MSG_RESULT_ERR;
+}
+
 static bool
 vq_is_ready(struct virtio_net *dev, struct vhost_virtqueue *vq)
 {
-- 
2.43.0

[PATCH v9 5/5] vhost_user: enable configure memory slots

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

This patch enables configure memory slots in the header define
VHOST_USER_PROTOCOL_FEATURES.

Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
---
 lib/vhost/vhost_user.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/vhost/vhost_user.h b/lib/vhost/vhost_user.h
index f8d921f7f1..5a0e747b58 100644
--- a/lib/vhost/vhost_user.h
+++ b/lib/vhost/vhost_user.h
@@ -32,6 +32,7 @@
 					 (1ULL << VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD) | \
 					 (1ULL << VHOST_USER_PROTOCOL_F_HOST_NOTIFIER) | \
 					 (1ULL << VHOST_USER_PROTOCOL_F_PAGEFAULT) | \
+					 (1ULL << VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS) | \
 					 (1ULL << VHOST_USER_PROTOCOL_F_STATUS))
 
 typedef enum VhostUserRequest {
-- 
2.43.0

Re: [PATCH v9 0/5] Support add/remove memory region and get-max-slots

[Stephen Hemminger]

On Tue, 7 Apr 2026 08:06:31 +0000
<pravin.bathija@dell.com> wrote:

> From: Pravin M Bathija <pravin.bathija@dell.com>
> 
> This is version v9 of the patchset and it incorporates the
> recommendations made by Stephen Hemminger.
> 
> Changes made to patch 3/5
> - Restored max_guest_pages initial value to hardcoded 8 instead of
>   VHOST_MEMORY_MAX_NREGIONS, matching upstream semantics.
> 
> Changes made to patch 4/5
> - Added close(reg->fd) and reg->fd = -1 before goto close_msg_fds in the
>   mmap failure path to fix fd leak after fd was moved from ctx->fds[0].
> - Converted dev_invalidate_vrings from a plain function to a macro +
>   implementation function pair, accepting message ID as a parameter so
>   the static_assert reports the correct handler at each call site.
> - Updated dev_invalidate_vrings call in add_mem_reg to pass
>   VHOST_USER_ADD_MEM_REG as message ID.
> - Updated dev_invalidate_vrings call in rem_mem_reg to pass
>   VHOST_USER_ADD_MEM_REG as message ID.
> 
> This implementation has been extensively tested by doing Read/Write I/O
> from multiple instances of fio + libblkio (front-end) talking to
> spdk/dpdk (back-end) based drives. Tested with qemu front-end talking to
> dpdk testpmd (back-end) performing add/removal of memory regions. Also
> tested post-copy live migration after doing add_memory_region.
> 
> Version Log:
> Version v9 (Current version): Incorporate code review suggestions from
> Stephen Hemminger as described above.
> Version v8:  Incorporate code review suggestions from Stephen Hemminger.
> rewrite async_dma_map_region function to iterate guest pages by host
> address range matching
> change function dev_invalidate_vrings to accept a double pointer to
> propagate pointer updates
> new function remove_guest_pages was added
> add_mem_reg error path was narrowed to only clean up the single failed
> region instead of destroting all existing regions
> Version v7: Incorporate code review suggestions from Maxime Coquelin.
> Add debug messages to vhost_postcopy_register function.
> Version v6: Added the enablement of this feature as a final patch in
> this patch-set and other code optimizations as suggested by Maxime
> Coquelin.
> Version v5: removed the patch that increased the number of memory regions
> from 8 to 128. This will be submitted as a separate feature at a later
> point after incorporating additional optimizations. Also includes code
> optimizations as suggested by Feng Cheng Wen.
> Version v4: code optimizations as suggested by Feng Cheng Wen.
> Version v3: code optimizations as suggested by Maxime Coquelin
> and Thomas Monjalon.
> Version v2: code optimizations as suggested by Maxime Coquelin.
> Version v1: Initial patch set.
> 
> Pravin M Bathija (5):
>   vhost: add user to mailmap and define to vhost hdr
>   vhost_user: header defines for add/rem mem region
>   vhost_user: support function defines for back-end
>   vhost_user: Function defs for add/rem mem regions
>   vhost_user: enable configure memory slots
> 
>  .mailmap               |   1 +
>  lib/vhost/rte_vhost.h  |   4 +
>  lib/vhost/vhost_user.c | 403 ++++++++++++++++++++++++++++++++++++-----
>  lib/vhost/vhost_user.h |  10 +
>  4 files changed, 375 insertions(+), 43 deletions(-)
> 

AI review is mostly clean now.

Patch series looks good overall. One issue in 4/5:
In rem_mem_reg, dev_invalidate_vrings (which calls
translate_ring_addresses) runs while the region being removed is still
mapped. Any vring address that resolves into that region will get a
pointer that becomes invalid after the subsequent
free_mem_region/munmap. Consider freeing the region first so translate
only sees surviving regions.

Also minor: the v9 cover letter changelog says rem_mem_reg passes
VHOST_USER_ADD_MEM_REG but the code correctly uses
VHOST_USER_REM_MEM_REG — just a typo in the changelog.

RE: [PATCH v9 0/5] Support add/remove memory region and get-max-slots

[Bathija, Pravin]

Dear Stephen,

The changes you suggested have been incorporated in the latest patch-set v10. Responses to comments inline.


Internal Use - Confidential
> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: Tuesday, April 7, 2026 7:21 AM
> To: Bathija, Pravin <Pravin.Bathija@dell.com>
> Cc: dev@dpdk.org; thomas@monjalon.net; maxime.coquelin@redhat.com;
> fengchengwen@huawei.com
> Subject: Re: [PATCH v9 0/5] Support add/remove memory region and get-max-
> slots
>
>
> [EXTERNAL EMAIL]
>
> On Tue, 7 Apr 2026 08:06:31 +0000
> <pravin.bathija@dell.com> wrote:
>
> > From: Pravin M Bathija <pravin.bathija@dell.com>
> >
> > This is version v9 of the patchset and it incorporates the
> > recommendations made by Stephen Hemminger.
> >
> > Changes made to patch 3/5
> > - Restored max_guest_pages initial value to hardcoded 8 instead of
> >   VHOST_MEMORY_MAX_NREGIONS, matching upstream semantics.
> >
> > Changes made to patch 4/5
> > - Added close(reg->fd) and reg->fd = -1 before goto close_msg_fds in the
> >   mmap failure path to fix fd leak after fd was moved from ctx->fds[0].
> > - Converted dev_invalidate_vrings from a plain function to a macro +
> >   implementation function pair, accepting message ID as a parameter so
> >   the static_assert reports the correct handler at each call site.
> > - Updated dev_invalidate_vrings call in add_mem_reg to pass
> >   VHOST_USER_ADD_MEM_REG as message ID.
> > - Updated dev_invalidate_vrings call in rem_mem_reg to pass
> >   VHOST_USER_ADD_MEM_REG as message ID.
> >
> > This implementation has been extensively tested by doing Read/Write
> > I/O from multiple instances of fio + libblkio (front-end) talking to
> > spdk/dpdk (back-end) based drives. Tested with qemu front-end talking
> > to dpdk testpmd (back-end) performing add/removal of memory regions.
> > Also tested post-copy live migration after doing add_memory_region.
> >
> > Version Log:
> > Version v9 (Current version): Incorporate code review suggestions from
> > Stephen Hemminger as described above.
> > Version v8:  Incorporate code review suggestions from Stephen Hemminger.
> > rewrite async_dma_map_region function to iterate guest pages by host
> > address range matching change function dev_invalidate_vrings to accept
> > a double pointer to propagate pointer updates new function
> > remove_guest_pages was added add_mem_reg error path was narrowed to
> > only clean up the single failed region instead of destroting all
> > existing regions Version v7: Incorporate code review suggestions from
> > Maxime Coquelin.
> > Add debug messages to vhost_postcopy_register function.
> > Version v6: Added the enablement of this feature as a final patch in
> > this patch-set and other code optimizations as suggested by Maxime
> > Coquelin.
> > Version v5: removed the patch that increased the number of memory
> > regions from 8 to 128. This will be submitted as a separate feature at
> > a later point after incorporating additional optimizations. Also
> > includes code optimizations as suggested by Feng Cheng Wen.
> > Version v4: code optimizations as suggested by Feng Cheng Wen.
> > Version v3: code optimizations as suggested by Maxime Coquelin and
> > Thomas Monjalon.
> > Version v2: code optimizations as suggested by Maxime Coquelin.
> > Version v1: Initial patch set.
> >
> > Pravin M Bathija (5):
> >   vhost: add user to mailmap and define to vhost hdr
> >   vhost_user: header defines for add/rem mem region
> >   vhost_user: support function defines for back-end
> >   vhost_user: Function defs for add/rem mem regions
> >   vhost_user: enable configure memory slots
> >
> >  .mailmap               |   1 +
> >  lib/vhost/rte_vhost.h  |   4 +
> >  lib/vhost/vhost_user.c | 403
> > ++++++++++++++++++++++++++++++++++++-----
> >  lib/vhost/vhost_user.h |  10 +
> >  4 files changed, 375 insertions(+), 43 deletions(-)
> >
>
> AI review is mostly clean now.
>
> Patch series looks good overall. One issue in 4/5:
> In rem_mem_reg, dev_invalidate_vrings (which calls
> translate_ring_addresses) runs while the region being removed is still mapped.
> Any vring address that resolves into that region will get a pointer that becomes
> invalid after the subsequent free_mem_region/munmap. Consider freeing the
> region first so translate only sees surviving regions.
>
Thanks for catching that — moved dev_invalidate_vrings after free_mem_region and the array compaction so that
translate_ring_addresses only sees surviving regions.

> Also minor: the v9 cover letter changelog says rem_mem_reg passes
> VHOST_USER_ADD_MEM_REG but the code correctly uses
> VHOST_USER_REM_MEM_REG — just a typo in the changelog.

Again good catch, made the edit to the cover letter.

[PATCH v9 0/5] Support add/remove memory region and get-max-slots

[pravin.bathija]

From: Pravin M Bathija <pravin.bathija@dell.com>

This is version v9 of the patchset and it incorporates the
recommendations made by Stephen Hemminger.

Changes made to patch 3/5
- Restored max_guest_pages initial value to hardcoded 8 instead of
  VHOST_MEMORY_MAX_NREGIONS, matching upstream semantics.

Changes made to patch 4/5
- Added close(reg->fd) and reg->fd = -1 before goto close_msg_fds in the
  mmap failure path to fix fd leak after fd was moved from ctx->fds[0].
- Converted dev_invalidate_vrings from a plain function to a macro +
  implementation function pair, accepting message ID as a parameter so
  the static_assert reports the correct handler at each call site.
- Updated dev_invalidate_vrings call in add_mem_reg to pass
  VHOST_USER_ADD_MEM_REG as message ID.
- Updated dev_invalidate_vrings call in rem_mem_reg to pass
  VHOST_USER_ADD_MEM_REG as message ID.

This implementation has been extensively tested by doing Read/Write I/O
from multiple instances of fio + libblkio (front-end) talking to
spdk/dpdk (back-end) based drives. Tested with qemu front-end talking to
dpdk testpmd (back-end) performing add/removal of memory regions. Also
tested post-copy live migration after doing add_memory_region.

Version Log:
Version v9 (Current version): Incorporate code review suggestions from
Stephen Hemminger as described above.
Version v8:  Incorporate code review suggestions from Stephen Hemminger.
rewrite async_dma_map_region function to iterate guest pages by host
address range matching
change function dev_invalidate_vrings to accept a double pointer to
propagate pointer updates 
new function remove_guest_pages was added
add_mem_reg error path was narrowed to only clean up the single failed
region instead of destroting all existing regions
Version v7: Incorporate code review suggestions from Maxime Coquelin.
Add debug messages to vhost_postcopy_register function.
Version v6: Added the enablement of this feature as a final patch in
this patch-set and other code optimizations as suggested by Maxime
Coquelin.
Version v5: removed the patch that increased the number of memory regions
from 8 to 128. This will be submitted as a separate feature at a later
point after incorporating additional optimizations. Also includes code
optimizations as suggested by Feng Cheng Wen.
Version v4: code optimizations as suggested by Feng Cheng Wen.
Version v3: code optimizations as suggested by Maxime Coquelin
and Thomas Monjalon.
Version v2: code optimizations as suggested by Maxime Coquelin.
Version v1: Initial patch set.

Pravin M Bathija (5):
  vhost: add user to mailmap and define to vhost hdr
  vhost_user: header defines for add/rem mem region
  vhost_user: support function defines for back-end
  vhost_user: Function defs for add/rem mem regions
  vhost_user: enable configure memory slots

 .mailmap               |   1 +
 lib/vhost/rte_vhost.h  |   4 +
 lib/vhost/vhost_user.c | 403 ++++++++++++++++++++++++++++++++++++-----
 lib/vhost/vhost_user.h |  10 +
 4 files changed, 375 insertions(+), 43 deletions(-)

-- 
2.43.0