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

[Burakov, Anatoly]

On 23-Aug-18 3:57 AM, Tiwei Bie wrote:
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: sta...@dpdk.org

Reported-by: Seán Harte <sea...@gmail.com>
Signed-off-by: Tiwei Bie <tiwei....@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;

There is a rte_memseg_list_walk() - please do not iterate over memseg 
lists manually.

  
-	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;
  }



--
Thanks,
Anatoly