Re: [PATCH v2 net-next 2/4] vmxnet3: add support to get/set rx flow hash

On 5/28/20, 12:21 PM, "Michal Kubecek" [off-list ref] wrote:

   On Thu, May 28, 2020 at 11:36:13AM -0700, Ronak Doshi wrote:
   > With vmxnet3 version 4, the emulation supports multiqueue(RSS) for
   > UDP and ESP traffic. A guest can enable/disable RSS for UDP/ESP over
   > IPv4/IPv6 by issuing commands introduced in this patch. ESP ipv6 is
   > not yet supported in this patch.
   > 
   > This patch implements get_rss_hash_opts and set_rss_hash_opts
   > methods to allow querying and configuring different Rx flow hash
   > configurations.
   > 
   > Signed-off-by: Ronak Doshi [off-list ref]
   > ---

   This still suffers from the inconsistency between get and set handler
  I already pointed out in v1:
  
   - there is no way to change VMXNET3_RSS_FIELDS_TCPIP{4,6} bits
   - get_rxnfc() may return value that set_rxnfc() won't accept
   - get_rxnfc() may return different value than set_rxnfc() set
   
   Above, vmxnet3_get_rss_hash_opts() returns 0 or
   RXH_L4_B_0_1 | RXH_L4_B_2_3 | RXH_IP_SRC | RXH_IP_DST for any of
   {TCP,UDP}_V{4,6}_FLOW, depending on corresponding bit in rss_fields. But
   here you accept only all four bits for TCP (both v4 and v6) and either
   the two RXH_IP_* bits or all four for UDP.
   
   Michal

 
Hi Michal,

That is intentional as vmxnet3 device always expects TCP rss to be enabled
if rss is supported. If RSS is enabled, by default rss_fields has TCP/IP RSS
supported and cannot be disabled. Its only for UDP/ESP flows the config
can change. Hence, get_rss always reports TCP/IP RSS enabled, and set_rss
does not accept disabling TCP RSS. Hope this answers your concern.

Thanks,
Ronak