Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934814AbcCPG06 (ORCPT ); Wed, 16 Mar 2016 02:26:58 -0400 Received: from [193.47.165.129] ([193.47.165.129]:36609 "EHLO mellanox.co.il" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1754569AbcCPG0y (ORCPT ); Wed, 16 Mar 2016 02:26:54 -0400 Date: Wed, 16 Mar 2016 08:09:47 +0200 From: Eli Cohen To: Alexey Kardashevskiy Cc: Or Gerlitz , Huy Nguyen , Doug Ledford , Eugenia Emantayev , Hal Rosenstock , Sean Hefty , Yishai Hadas , Linux Kernel , "linux-rdma@vger.kernel.org" , Linux Netdev List , Paul Mackerras , Carol L Soto , Yevgeny Petrilin , Brian J King Subject: Re: [RFC PATCH kernel] Revert "net/mlx4_core: Set UAR page size to 4KB regardless of system page size" Message-ID: <20160316060947.GD66645@x-vnc01.mtx.labs.mlnx> References: <1458037148-4475-1-git-send-email-aik@ozlabs.ru> <56E8BFFE.9000803@ozlabs.ru> <20160316051021.GC66645@x-vnc01.mtx.labs.mlnx> <56E8F3CC.3070203@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56E8F3CC.3070203@ozlabs.ru> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2128 Lines: 54 On Wed, Mar 16, 2016 at 04:49:00PM +1100, Alexey Kardashevskiy wrote: > On 03/16/2016 04:10 PM, Eli Cohen wrote: > >On Wed, Mar 16, 2016 at 01:07:58PM +1100, Alexey Kardashevskiy wrote: > >> > >>So with v4.5 as a host, there is no actual distro available today to > >>use as a guest in the next 6 months (or whatever it takes to > >>backport this partucular patch back there). > >> > >>You could have added a module parameter to enforce the old behavoir, > >>at least... > >> > >>And sorry but from the original commit log I could not understand > >>why exactly all existing guests need to be broken. Could you please > >>point me to a piece of documentation describing all this UAR > >>bisuness (what is UAR, why 128 UARs are required and for what, etc). > >>Thanks. > >> > > > >We are going to send a patch that fixes this using a module parameter. > >The patch will be on top of Huy's patch. > > > >Some background to the problem: mlx4 supported devices require 128 UAR > > What does UAR stand for? User Access Region. It's the way you interface with the hardware. > > >pages from PCI memory space defined by BAR2-3. Each UAR page can be > >any power of 2 value from 4K up to 64K. Before Huy's patch the driver > >chose UAR page size to be equal to system page size. Since PowerPC's > >page size is 64K this means minimum requirement of UAR pages is not > >met (default UAR BAR is 8MB and only half of it is really reserved for > >UARs). > > And what was the downside? afaict the performance was good... > It's not a performance issue. Defining 64KB for a UAR is not required and wastes pci memory mapped i/o space. > > >More details can be found in the programmer's manual. > > Can you please point me to this manual on the website? I tried, > honestly, could not find it. Thanks. > It's not publically available. If you have an FAE that work with your company you can ask him how to get the doc. > > -- > Alexey > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html