From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: [PATCH rdma-next V1 1/9] IB/ipoib: Add warning message when changing the MTU in UD over the max range Date: Sun, 15 Jan 2017 10:35:43 +0200 Message-ID: <20170115083543.GA20392@mtr-leonro.local> References: <20161228124728.26619-1-leon@kernel.org> <20161228124728.26619-2-leon@kernel.org> <1484246776.123135.19.camel@redhat.com> <20170112193508.GO20392@mtr-leonro.local> <20170112201622.GA14584@obsidianresearch.com> <20170113150824.GQ20392@mtr-leonro.local> <20170113171234.GA30551@obsidianresearch.com> <20170113203127.GT20392@mtr-leonro.local> <20170113212721.GB1463@obsidianresearch.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="+mSjbC2tVdWE/Wop" Return-path: Content-Disposition: inline In-Reply-To: <20170113212721.GB1463-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Doug Ledford , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Feras Daoud , Noa Osherovich List-Id: linux-rdma@vger.kernel.org --+mSjbC2tVdWE/Wop Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jan 13, 2017 at 02:27:21PM -0700, Jason Gunthorpe wrote: > On Fri, Jan 13, 2017 at 10:31:27PM +0200, Leon Romanovsky wrote: > > > > This is about what happens if the multicast MTU < unicast MTU - which > > > is *exactly* the same case on RC and UD. > > > > > > IPoIB cannot send a 64k multicast MTU on RC either. > > > > Multicast is sent in datagram despite being in connected mode and for > > datagram the MTU is limited by IB > > I am aware of that. Read you patch again: > > > + if (priv->mcast_mtu < priv->admin_mtu) > > + ipoib_warn(priv, "MTU must be smaller than mcast_mtu (%u)\n", > > This check is fails in RC mode as well. > > And we already check if the requested MTU is beyond the port > capability: > > + if (new_mtu > IPOIB_UD_MTU(priv->max_ib_mtu)) > + return -EINVAL; > > So I have *no idea* why you'd want to check it against the multicast > group too.. > Port MTU capability can be higher than link MTU. In this flow, the user can try to set manually MTU which will be higher than SM provided. Immediately after that print, we have a following piece of code: 236 dev->mtu = min(priv->mcast_mtu, priv->admin_mtu); > It is OK for the multicast group to have a smaller MTU than the > unicast side. This is how RC operates after all. > > Jason --+mSjbC2tVdWE/Wop Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkhr/r4Op1/04yqaB5GN7iDZyWKcFAlh7NF8ACgkQ5GN7iDZy WKfVAQ//VG7YsAjKSXz0kZHVe2ekktOotWamPU1A49H7NThGA6HB05W4ci8kuYwO /hRxnMoXJczrPJrgZr6sJXALr1E63sJzaTFpG0o+O2d3HaYAS/dh9WhGV/amfBj+ ExI/O0071e5sybYXpQ/876h/F7vsWC65WxVPhIc0GoUsPTHduVaY+onGEgEokqYP vNhDjl0XiI8AMoyr/33iIQ9IMJO4+ZnGkvkJqR8jwf77XJM5gubx/OxkG1OS/N36 FxXyKzjLSDGWobO1viVtQpVlYD9u83ZR0UGU0MU+i65QOf6ZpxuwIVk/s1dpUiss D4ZM/uJKk9rfcJFD4ImplEVPZJB0pO3p0DLGqJRT5n5GbBp/BF63ydoQl9CUc5tl x4gfXe2gBL9LAv124qrXOzqLWJUxaedmpoAVtTkqN2bFAf3fmhfY7O0DC43c7O0S p0u7hFm6RYXAu7pD3AC1+KofaoRpR/gZGK6VXh9EoxgzYp7vqGCFaEJCtN8EjI9T DlZq39X39DtqHvTUpLUi7GpF3Iep6+F13sckk4BoQ+foO1s3uktI2On2XWnAkbkp mtd4yd+NOXdpqTcQXVBU9qN87KSXxhKqM/xBmVjybqq6oRQ1Ru0+cLQWnPfgOs7i UdhcZuyMjErbQ+HVnCCXjmaA+O3z7KpJdqMNEdzlrAPrmAdfEuA= =x6Ey -----END PGP SIGNATURE----- --+mSjbC2tVdWE/Wop-- -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html