[PATCH] example: vdpa: support run in nested virtualization environment

[PATCH] example: vdpa: support run in nested virtualization environment

[Hao Chen]

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
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.

Signed-off-by: Hao Chen <chenh@yusur.tech>
---
 examples/vdpa/main.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
index 4c7e81d7b6..a24c78d7a4 100644
--- a/examples/vdpa/main.c
+++ b/examples/vdpa/main.c
@@ -43,16 +43,20 @@ 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);
+	printf("Usage: %s [EAL options] --\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, "%s", usage_str);
+	exit(1);
 }
 
 static int
@@ -63,6 +67,7 @@ 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 +225,10 @@ 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,
-- 
2.27.0

RE: [PATCH] example: vdpa: support run in nested virtualization environment

[Xia, Chenbo]

> -----Original Message-----
> From: Hao Chen <chenh@yusur.tech>
> Sent: Tuesday, October 11, 2022 10:56 AM
> To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; houyl@yusur.tech; zy@yusur.tech
> Subject: [PATCH] example: vdpa: support run in nested virtualization
> environment

Title should be:

examples/vdpa: support running in nested virtualization environment

> 
> 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
> 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.
> 
> Signed-off-by: Hao Chen <chenh@yusur.tech>
> ---
>  examples/vdpa/main.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
> index 4c7e81d7b6..a24c78d7a4 100644
> --- a/examples/vdpa/main.c
> +++ b/examples/vdpa/main.c
> @@ -43,16 +43,20 @@ 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);
> +	printf("Usage: %s [EAL options] --\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, "%s", usage_str);

Why not use fprintf all string including the eal one?

> +	exit(1);

I believe the exit should happen outside of the function.

Thanks,
Chenbo

>  }
> 
>  static int
> @@ -63,6 +67,7 @@ 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 +225,10 @@ 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,
> --
> 2.27.0

[PATCH v2] example: vdpa: support run in nested virtualization environment

[Hao Chen]

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
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.

Signed-off-by: Hao Chen <chenh@yusur.tech>
---
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,
-- 
2.27.0

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

[Hao Chen]

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
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.

Signed-off-by: Hao Chen <chenh@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,
-- 
2.27.0

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

[Maxime Coquelin]

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 <chenh@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,

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 <chenh@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,
>

[PATCH v4] examples/vdpa: support running in nested virtualization environment

[Hao Chen]

When we run dpdk vdpa in the nested virtual machine vm-L1 and ping
test in vm-L2, the ping is not good. The reason for troubleshooting is
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 flag RTE_VHOST_USER_IOMMU_SUPPORT to use vhost vIOMMU
, VIRTIO_F_IOMMU_PLATFORM feature will be negotiated successfully if
virtio iommu is used in a nested virtualization environment.

The configuration is as follows:
The host starts iommu, and the kernel parameter is added with
'intel_iommu=on iommu=pt'.
VM-L1's xml add viommu and virtio device adds iommu='on' ats='on'.
VM-L2's xml enables viommu, and adds  parameters
'intel_iommu=on iommu=pt' to kernel.

Then the ping test in vm-L2 is OK.

Signed-off-by: Hao Chen <chenh@yusur.tech>
---
v4:
*Simplify the patch. Set the flags RTE_VHOST_USER_IOMMU_SUPPORT default.

v3:
*Modify mail title.

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

 examples/vdpa/main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
index 4c7e81d7b6..4d3203f3a7 100644
--- a/examples/vdpa/main.c
+++ b/examples/vdpa/main.c
@@ -214,6 +214,8 @@ start_vdpa(struct vdpa_port *vport)
 	if (client_mode)
 		vport->flags |= RTE_VHOST_USER_CLIENT;
 
+	vport->flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
+
 	if (access(socket_path, F_OK) != -1 && !client_mode) {
 		RTE_LOG(ERR, VDPA,
 			"%s exists, please remove it or specify another file and try again.\n",
-- 
2.27.0

Re: [PATCH v4] examples/vdpa: support running in nested virtualization environment

[Maxime Coquelin]

On 11/14/22 04:04, Hao Chen wrote:
> When we run dpdk vdpa in the nested virtual machine vm-L1 and ping
> test in vm-L2, the ping is not good. The reason for troubleshooting is
> 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 flag RTE_VHOST_USER_IOMMU_SUPPORT to use vhost vIOMMU
> , VIRTIO_F_IOMMU_PLATFORM feature will be negotiated successfully if
> virtio iommu is used in a nested virtualization environment.
> 
> The configuration is as follows:
> The host starts iommu, and the kernel parameter is added with
> 'intel_iommu=on iommu=pt'.
> VM-L1's xml add viommu and virtio device adds iommu='on' ats='on'.
> VM-L2's xml enables viommu, and adds  parameters
> 'intel_iommu=on iommu=pt' to kernel.
> 
> Then the ping test in vm-L2 is OK.
> 
> Signed-off-by: Hao Chen <chenh@yusur.tech>
> ---
> v4:
> *Simplify the patch. Set the flags RTE_VHOST_USER_IOMMU_SUPPORT default.
> 
> v3:
> *Modify mail title.
> 
> v2:
> *fprintf all string including the eal one.
> *remove exit(1).
> 
>   examples/vdpa/main.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
> index 4c7e81d7b6..4d3203f3a7 100644
> --- a/examples/vdpa/main.c
> +++ b/examples/vdpa/main.c
> @@ -214,6 +214,8 @@ start_vdpa(struct vdpa_port *vport)
>   	if (client_mode)
>   		vport->flags |= RTE_VHOST_USER_CLIENT;
>   
> +	vport->flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
> +
>   	if (access(socket_path, F_OK) != -1 && !client_mode) {
>   		RTE_LOG(ERR, VDPA,
>   			"%s exists, please remove it or specify another file and try again.\n",

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime

Re: [PATCH v4] examples/vdpa: support running in nested virtualization environment

[Maxime Coquelin]

On 11/14/22 04:04, Hao Chen wrote:
> When we run dpdk vdpa in the nested virtual machine vm-L1 and ping
> test in vm-L2, the ping is not good. The reason for troubleshooting is
> 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 flag RTE_VHOST_USER_IOMMU_SUPPORT to use vhost vIOMMU
> , VIRTIO_F_IOMMU_PLATFORM feature will be negotiated successfully if
> virtio iommu is used in a nested virtualization environment.
> 
> The configuration is as follows:
> The host starts iommu, and the kernel parameter is added with
> 'intel_iommu=on iommu=pt'.
> VM-L1's xml add viommu and virtio device adds iommu='on' ats='on'.
> VM-L2's xml enables viommu, and adds  parameters
> 'intel_iommu=on iommu=pt' to kernel.
> 
> Then the ping test in vm-L2 is OK.
> 
> Signed-off-by: Hao Chen <chenh@yusur.tech>
> ---
> v4:
> *Simplify the patch. Set the flags RTE_VHOST_USER_IOMMU_SUPPORT default.
> 
> v3:
> *Modify mail title.
> 
> v2:
> *fprintf all string including the eal one.
> *remove exit(1).
> 
>   examples/vdpa/main.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/examples/vdpa/main.c b/examples/vdpa/main.c
> index 4c7e81d7b6..4d3203f3a7 100644
> --- a/examples/vdpa/main.c
> +++ b/examples/vdpa/main.c
> @@ -214,6 +214,8 @@ start_vdpa(struct vdpa_port *vport)
>   	if (client_mode)
>   		vport->flags |= RTE_VHOST_USER_CLIENT;
>   
> +	vport->flags |= RTE_VHOST_USER_IOMMU_SUPPORT;
> +
>   	if (access(socket_path, F_OK) != -1 && !client_mode) {
>   		RTE_LOG(ERR, VDPA,
>   			"%s exists, please remove it or specify another file and try again.\n",


Applied to dpdk-next-virtio/main.

Thanks,
Maxime