[dpdk-dev] [PATCH] net/virtio-user: fix memory hotplug support

[Tiwei Bie <tiwei.bie@intel.com>]

Deadlock can occur when allocating memory if a vhost-kernel
based virtio-user device is in use. Besides, it's possible
to have much more than 64 non-contiguous hugepage backed
memory regions due to the memory hotplug, which may cause
problems when handling VHOST_SET_MEM_TABLE request. A better
solution is to have the virtio-user pass all the VA ranges
reserved by DPDK to vhost-kernel.

Bugzilla ID: 81
Fixes: 12ecb2f63b12 ("net/virtio-user: support memory hotplug")
Cc: stable@dpdk.org

Reported-by: Seán Harte <seanbh@gmail.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
---
 drivers/net/virtio/virtio_user/vhost_kernel.c | 64 ++++++++-----------
 1 file changed, 27 insertions(+), 37 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c b/drivers/net/virtio/virtio_user/vhost_kernel.c
index b2444096c..49bd1b821 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
@@ -70,41 +70,12 @@ static uint64_t vhost_req_user_to_kernel[] = {
 	[VHOST_USER_SET_MEM_TABLE] = VHOST_SET_MEM_TABLE,
 };
 
-struct walk_arg {
-	struct vhost_memory_kernel *vm;
-	uint32_t region_nr;
-};
-static int
-add_memory_region(const struct rte_memseg_list *msl __rte_unused,
-		const struct rte_memseg *ms, size_t len, void *arg)
-{
-	struct walk_arg *wa = arg;
-	struct vhost_memory_region *mr;
-	void *start_addr;
-
-	if (wa->region_nr >= max_regions)
-		return -1;
-
-	mr = &wa->vm->regions[wa->region_nr++];
-	start_addr = ms->addr;
-
-	mr->guest_phys_addr = (uint64_t)(uintptr_t)start_addr;
-	mr->userspace_addr = (uint64_t)(uintptr_t)start_addr;
-	mr->memory_size = len;
-	mr->mmap_offset = 0;
-
-	return 0;
-}
-
-/* By default, vhost kernel module allows 64 regions, but DPDK allows
- * 256 segments. As a relief, below function merges those virtually
- * adjacent memsegs into one region.
- */
 static struct vhost_memory_kernel *
 prepare_vhost_memory_kernel(void)
 {
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
 	struct vhost_memory_kernel *vm;
-	struct walk_arg wa;
+	uint32_t region_nr = 0, i;
 
 	vm = malloc(sizeof(struct vhost_memory_kernel) +
 			max_regions *
@@ -112,15 +83,34 @@ prepare_vhost_memory_kernel(void)
 	if (!vm)
 		return NULL;
 
-	wa.region_nr = 0;
-	wa.vm = vm;
+	for (i = 0; i < RTE_MAX_MEMSEG_LISTS; i++) {
+		struct rte_memseg_list *msl = &mcfg->memsegs[i];
+		struct vhost_memory_region *mr;
+		void *start_addr;
+		uint64_t len;
 
-	if (rte_memseg_contig_walk(add_memory_region, &wa) < 0) {
-		free(vm);
-		return NULL;
+		start_addr = msl->base_va;
+		len = msl->page_sz * msl->memseg_arr.len;
+
+		if (start_addr == NULL || len == 0)
+			continue;
+
+		if (region_nr >= max_regions) {
+			free(vm);
+			return NULL;
+		}
+
+		mr = &vm->regions[region_nr++];
+		mr->guest_phys_addr = (uint64_t)(uintptr_t)start_addr;
+		mr->userspace_addr = (uint64_t)(uintptr_t)start_addr;
+		mr->memory_size = len;
+		mr->mmap_offset = 0; /* flags_padding */
+
+		PMD_DRV_LOG(DEBUG, "index=%u, addr=%p len=%" PRIu64,
+				i, start_addr, len);
 	}
 
-	vm->nregions = wa.region_nr;
+	vm->nregions = region_nr;
 	vm->padding = 0;
 	return vm;
 }
-- 
2.18.0