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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id d25sm3518972qko.96.2019.07.12.08.14.23 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 12 Jul 2019 08:14:23 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hlxFf-0002BK-4s; Fri, 12 Jul 2019 12:14:23 -0300 Date: Fri, 12 Jul 2019 12:14:23 -0300 From: Jason Gunthorpe To: Arnd Bergmann Cc: Bernard Metzler , Doug Ledford , Peter Zijlstra , linux-rdma , Linux Kernel Mailing List Subject: Re: Re: [PATCH] rdma/siw: avoid smp_store_mb() on a u64 Message-ID: <20190712151423.GG27512@ziepe.ca> References: <20190712085212.3901785-1-arnd@arndb.de> <20190712120328.GB27512@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Fri, Jul 12, 2019 at 03:22:35PM +0200, Arnd Bergmann wrote: > On Fri, Jul 12, 2019 at 3:05 PM Bernard Metzler wrote: > > > > > We share CQ (completion queue) notification flags between application > > (which may be user land) and producer (kernel QP's (queue pairs)). > > Those flags can be written by both application and QP's. The application > > writes those flags to let the driver know if it shall inform about new > > work completions. It can write those flags at any time. > > Only a kernel producer reads those flags to decide if > > the CQ notification handler shall be kicked, if a new CQ element gets > > added to the CQ. When kicking the completion handler, the driver resets the > > notification flag, which must get re-armed by the application. > > > > We use READ_ONCE() and WRITE_ONCE(), since the flags are potentially > > shared (mmap'd) between user and kernel land. > > > > siw_req_notify_cq() is being called only by kernel consumers to change > > (write) the CQ notification state. We use smp_store_mb() to make sure > > the new value becomes visible to all kernel producers (QP's) asap. > > > > > > From cfb861a09dcfb24a98ba0f1e26bdaa1529d1b006 Mon Sep 17 00:00:00 2001 > > From: Bernard Metzler > > Date: Fri, 12 Jul 2019 13:19:27 +0200 > > Subject: [PATCH] Make shared CQ notification flags 32bit to respect 32bit > > architectures > > > > Signed-off-by: Bernard Metzler > > This fixes the build for me, thanks! > > Tested-by: Arnd Bergmann Since this is coming up so late in the merge window, I'm inclined to take the simple path while Bernard makes a complete solution here. What do you think Arnd? >From 0b043644c0ca601cb19943a81aa1f1455dbe9461 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Fri, 12 Jul 2019 12:12:06 -0300 Subject: [PATCH] RMDA/siw: Require a 64 bit arch The new siw driver fails to build on i386 with drivers/infiniband/sw/siw/siw_qp.c:1025:3: error: invalid output size for constraint '+q' smp_store_mb(*cq->notify, SIW_NOTIFY_NOT); As it is using 64 bit values with the smp_store_mb. Since the entire scheme here seems questionable, and we are in the merge window, fix the compile failures by disabling 32 bit support on this driver. A proper fix will be reviewed post merge window. Fixes: c0cf5bdde46c ("rdma/siw: addition to kernel build environment") Reported-by: Arnd Bergmann Signed-off-by: Jason Gunthorpe --- drivers/infiniband/sw/siw/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/infiniband/sw/siw/Kconfig b/drivers/infiniband/sw/siw/Kconfig index b622fc62f2cd6d..dace276aea1413 100644 --- a/drivers/infiniband/sw/siw/Kconfig +++ b/drivers/infiniband/sw/siw/Kconfig @@ -1,6 +1,6 @@ config RDMA_SIW tristate "Software RDMA over TCP/IP (iWARP) driver" - depends on INET && INFINIBAND && LIBCRC32C + depends on INET && INFINIBAND && LIBCRC32C && 64BIT select DMA_VIRT_OPS help This driver implements the iWARP RDMA transport over -- 2.21.0