[ofa-general] [PATCHv2] IB/ipoib: S/G and HW checksum support

[Michael S. Tsirkin]

> Quoting Or Gerlitz <ogerlitz at voltaire.com>:
> Subject: Re: [ofa-general] [PATCHv2] IB/ipoib: S/G and HW checksum support
> 
> Michael S. Tsirkin wrote:
> >Add module option hw_csum: when set, IPoIB will report S/G
> >support, and rely on hardware end-to-end transport checksum (ICRC)
> >instead of software-level protocol checksums.
> 
> >Since this will not inter-operate with older IPoIB modules,
> >this option is off by default.
> 
> Hi Michael,
> 
> looking on slide 18 of Dror's Sonoma presentation (*) which states -
> 
> >Checksum Offload
> >TCP/UDP/IP Checksum Offloading - Query device for checksum offload support
> >QP Creation - Mark QP for IPoIB checksum support
> >TX - ibv_send_flags indicate checksum offload request
> >RX - ibv_wc_flags indicate checksum status (good, bad, unverified)

All this is only supported by connectx and only for datagram (not ipoib cm).

> I don't see that there is such dependency, nor I can understand the 
> design that creates the dependency, unless you rely on the IB CRC and 
> not compute the actual TCP/UDP/IP csum.

Your question is moot. I'll just quote the commit message here:
	rely on hardware end-to-end transport checksum (ICRC)
	instead of software-level protocol checksums

While this does not inter-operate with standard ipoib RFC,
all TCP/IP suite protocols work as usual, so I think that
this is at least as useful as SDP is.

-- 
MST