net/vhost: restore pseudo TSO support

The net/vhost pmd does not comply with the ethdev offload API as it does
not report rx/tx offload capabilities wrt TSO and checksum offloading.
On the other hand, the net/vhost pmd lets guest negotiates TSO and
checksum offloading.

Changing the behavior for rx/tx offload flags handling won't
improve/fix this situation and will break applications that might have
been relying on implicit support of TSO in this driver.

Revert this behavior change until we have a complete fix.

Fixes: ca7036b4af3a ("vhost: fix offload flags in Rx path")

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
The full fix requires:
- reporting rx/tx_offload_capa,
- supporting sw TSO and checksums for the case when a virtual machine
  negotiates this feature, but the application does not configure
  DEV_[RT]X_OFFLOAD_* appropriate flags,

---
 drivers/net/vhost/rte_eth_vhost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Hi David,

On 5/18/21 9:07 AM, David Marchand wrote:
> The net/vhost pmd does not comply with the ethdev offload API as it does
> not report rx/tx offload capabilities wrt TSO and checksum offloading.
> On the other hand, the net/vhost pmd lets guest negotiates TSO and
> checksum offloading.
> 
> Changing the behavior for rx/tx offload flags handling won't
> improve/fix this situation and will break applications that might have
> been relying on implicit support of TSO in this driver.
> 
> Revert this behavior change until we have a complete fix.
> 
> Fixes: ca7036b4af3a ("vhost: fix offload flags in Rx path")
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
> The full fix requires:
> - reporting rx/tx_offload_capa,
> - supporting sw TSO and checksums for the case when a virtual machine
>   negotiates this feature, but the application does not configure
>   DEV_[RT]X_OFFLOAD_* appropriate flags,
> 
> ---
>  drivers/net/vhost/rte_eth_vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
> index 8524898661..a202931e9a 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -1505,7 +1505,7 @@ rte_pmd_vhost_probe(struct rte_vdev_device *dev)
>  	int ret = 0;
>  	char *iface_name;
>  	uint16_t queues;
> -	uint64_t flags = RTE_VHOST_USER_NET_COMPLIANT_OL_FLAGS;
> +	uint64_t flags = 0;
>  	uint64_t disable_flags = 0;
>  	int client_mode = 0;
>  	int iommu_support = 0;
> 

As we discussed yesterday, I agree that's the best thing to do while
proper TSO support is implemented.

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

Thanks,
Maxime

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Tuesday, May 18, 2021 3:07 PM
> To: dev@dpdk.org
> Cc: thomas@monjalon.net; Yigit, Ferruh <ferruh.yigit@intel.com>; Maxime
> Coquelin <maxime.coquelin@redhat.com>; Xia, Chenbo <chenbo.xia@intel.com>
> Subject: [PATCH] net/vhost: restore pseudo TSO support
> 
> The net/vhost pmd does not comply with the ethdev offload API as it does
> not report rx/tx offload capabilities wrt TSO and checksum offloading.
> On the other hand, the net/vhost pmd lets guest negotiates TSO and
> checksum offloading.
> 
> Changing the behavior for rx/tx offload flags handling won't
> improve/fix this situation and will break applications that might have
> been relying on implicit support of TSO in this driver.
> 
> Revert this behavior change until we have a complete fix.
> 
> Fixes: ca7036b4af3a ("vhost: fix offload flags in Rx path")
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
> 2.23.0

Applied to next-virtio/main. Thanks.