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.

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?


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,


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