On Tue, May 29, 2018 at 06:16:14PM +0200, Håkon Bugge wrote: > > > On 29 May 2018, at 17:49, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote: > >> The agent TID is a 64 bit value split in two dwords. The least > >> significant dword is the TID running counter. The most significant > >> dword is the agent number. In the CX-3 shared port model, the mlx4 > >> driver uses the most significant byte of the agent number to store the > >> slave number, making agent numbers greater and equal to 2^24 (3 bytes) > >> unusable. > > > > There is no reason for this to be an ida, just do something like > > > > mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id) & mad_agent_priv->ib_dev->tid_mask; > > > > And have the driver set tid_mask to 3 bytes of 0xFF > > The issue is that some of the mad agents are long-lived, so you will > wrap and use the same TID twice. We already have that problem, and using ida is problematic because we need to maximize the time between TID re-use, which ida isn't doing. Preventing re-use seems like a seperate issue from limiting the range to be compatible with mlx4. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
