On 11/11/21 19:06, Paolo Valerio wrote:
> Hi Chris,
>
> Chris Mi via dev <[email protected]> writes:
>
>> OVS_DP_F_UNALIGNED is already set, no need to set again. If restarting ovs,
>> dp is already created. So dpif_netlink_dp_transact() will return EEXIST.
>> No need to probe again.
>>
>> Signed-off-by: Chris Mi <[email protected]>
>> ---
>> lib/dpif-netlink.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c
>> index 5f4b60c5a..baa8e4d2a 100644
>> --- a/lib/dpif-netlink.c
>> +++ b/lib/dpif-netlink.c
>> @@ -411,11 +411,10 @@ dpif_netlink_open(const struct dpif_class *class
>> OVS_UNUSED, const char *name,
>> * dispatching, we fall back to the per-vport dispatch mode.
>> */
>> dp_request.user_features &= ~OVS_DP_F_UNSUPPORTED;
>> - dp_request.user_features |= OVS_DP_F_UNALIGNED;
>> dp_request.user_features &= ~OVS_DP_F_VPORT_PIDS;
>> dp_request.user_features |= OVS_DP_F_DISPATCH_UPCALL_PER_CPU;
>> error = dpif_netlink_dp_transact(&dp_request, &dp, &buf);
>> - if (error) {
>> + if (error == EOPNOTSUPP) {
>> dp_request.user_features &= ~OVS_DP_F_DISPATCH_UPCALL_PER_CPU;
>> dp_request.user_features |= OVS_DP_F_VPORT_PIDS;
>> error = dpif_netlink_dp_transact(&dp_request, &dp, &buf);
>
> The patch LGTM, there's a remark about this function, though.
Paolo, should I consider this as 'Acked-by' ?
>
> Before [1] the datapath did not check what user_features were supported,
> for this reason [2] was needed to avoid the case in which we set
> OVS_DP_F_DISPATCH_UPCALL_PER_CPU on old kernels without supporting it.
>
> I wonder what happens if, in case of kernel without [1] (prior to
> 5.4), we try to create the datapath during a restart?
>
> My impression is that we'll keep transacting receiving EEXIST, and only
> after opening (without trying to create it) we set the things as we
> intend.
>
> This seems to be confirmed by:
>
> ovs-vswitchd 834 [000] 146.180045: probe:ovs_dp_cmd_new__return:
> (ffffffffc075d290 <- ffffffffacba1a5a) retval=0xffffffef
> ovs-vswitchd 834 [000] 146.180111: probe:ovs_dp_cmd_new__return:
> (ffffffffc075d290 <- ffffffffacba1a5a) retval=0xffffffef
> ovs-vswitchd 834 [000] 146.180212: probe:ovs_dp_cmd_new__return:
> (ffffffffc075d290 <- ffffffffacba1a5a) retval=0xffffffef
>
> Note that I didn't really test it against an old kernel, but I just
> removed the user_features validation from the kernel code.
>
> If confirmed, this is not a problem per se (there should not be a case
> where this can become a functional problem), it's more about knowing that
> there's this further chance to clean things up.
>
> [1] 95a7233c452a ("net: openvswitch: Set OvS recirc_id from tc chain index")
> [2] b841e3cd4a28 ("dpif-netlink: Fix feature negotiation for older kernels.")
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