Re: [PATCH v3] examples/vdpa: support running in nested virtualization environment

[Hao Chen]

On 2022/10/26 14:10, Maxime Coquelin wrote:
Hi Hao

On 10/25/22 08:19, Hao Chen wrote:
When we run dpdk vdpa in the nested virtual machine vm-L1 and ping
test in vm-L2, the ping is NG. The reason for troubleshooting is

NG == not good? Please don't use abbreviations.

Yes, I will pay attention to this later.
that the virtio net in vm-L2 sends control information to the vring,
and the qemu back-end device in vm-L1 cannot obtain correct data
from the vring. This problem is related to the opening of the vIOMMU.

This patch add option '--iommu-support' to use guest vIOMMU to
protect vhost, then the ping test in vm-L2 is OK.
This option is required in a nested virtualization environment.

I'm wondering whether the flag shouldn't just be set by default, as the
feature negotiation will be done between the vDPA driver & the guest
driver anyways?

Yes, It can be set by default rather than as an option. 
VIRTIO_F_IOMMU_PLATFORM feature will not be negotiated successfully if 
it is not in a nested virtualization environment.

I will simplify the patch.

Thanks.

Signed-off-by: Hao Chen <ch...@yusur.tech>
---
v3:
*Modify mail title.

v2:
*fprintf all string including the eal one.
*remove exit(1).

  examples/vdpa/main.c | 17 ++++++++++++-----
  1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
index 4c7e81d7b6..71149461c6 100644
--- a/examples/vdpa/main.c
+++ b/examples/vdpa/main.c
@@ -43,16 +43,18 @@ static char iface[MAX_PATH_LEN];
  static int devcnt;
  static int interactive;
  static int client_mode;
+static int iommu_support;
    /* display usage */
  static void
  vdpa_usage(const char *prgname)
  {
-    printf("Usage: %s [EAL options] -- "
-                 "    --interactive|-i: run in interactive mode.\n"
-                 "    --iface <path>: specify the path prefix of the 
socket files, e.g. /tmp/vhost-user-.\n"
-                 "    --client: register a vhost-user socket as 
client mode.\n",
-                 prgname);
+    const char *usage_str = "    --interactive|-i: run in 
interactive mode.\n"
+                "    --iface <path>: specify the path prefix of the 
socket files, e.g. /tmp/vhost-user-.\n"
+                "    --client: register a vhost-user socket as 
client mode.\n"
+                "    --iommu-support: use guest vIOMMU to protect 
vhost.\n";
+
+    fprintf(stderr, "Usage: %s [EAL options] --\n%s", prgname, 
usage_str);
  }
    static int
@@ -63,6 +65,7 @@ parse_args(int argc, char **argv)
          {"iface", required_argument, NULL, 0},
          {"interactive", no_argument, &interactive, 1},
          {"client", no_argument, &client_mode, 1},
+        {"iommu-support", no_argument, &iommu_support, 1},
          {NULL, 0, 0, 0},
      };
      int opt, idx;
@@ -220,6 +223,10 @@ start_vdpa(struct vdpa_port *vport)
              socket_path);
          return -1;
      }
+
+    if (iommu_support)
+        vport->flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
+
      ret = rte_vhost_driver_register(socket_path, vport->flags);
      if (ret != 0)
          rte_exit(EXIT_FAILURE,