From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: To: Jens Axboe , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm@lists.01.org, linux-block@vger.kernel.org References: <20180830185352.3369-1-logang@deltatee.com> <20180830185352.3369-8-logang@deltatee.com> From: Logan Gunthorpe Message-ID: <7c5b9d2c-d94e-582c-f1d7-0827dbb7df7c@deltatee.com> Date: Thu, 30 Aug 2018 13:17:40 -0600 MIME-Version: 1.0 In-Reply-To: Subject: Re: [PATCH v5 07/13] block: Add PCI P2P flag for request queue and check support for requests List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sagi Grimberg , =?UTF-8?Q?Christian_K=c3=b6nig?= , Benjamin Herrenschmidt , Alex Williamson , Stephen Bates , Keith Busch , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Bjorn Helgaas , Max Gurtovoy , Dan Williams , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+bjorn=helgaas.com@lists.infradead.org List-ID: On 30/08/18 01:11 PM, Jens Axboe wrote: > On 8/30/18 12:53 PM, Logan Gunthorpe wrote: >> QUEUE_FLAG_PCI_P2P is introduced meaning a driver's request queue >> supports targeting P2P memory. >> >> When a request is submitted we check if PCI P2PDMA memory is assigned >> to the first page in the bio. If it is, we ensure the queue it's >> submitted to supports it, and enforce REQ_NOMERGE. > > I think this belongs in the caller - both the validity check, and > passing in NOMERGE for this type of request. I don't want to impose > this overhead on everything, for a pretty niche case. Well, the point was to prevent driver writers from doing the wrong thing. The WARN_ON would be a bit pointless in the driver if we rely on the driver to either do the right thing or add the WARN_ON themselves. If I'm going to change anything I'd drop the warning entirely and move the NO_MERGE back into the caller... Note: the check will be compiled out if the kernel does not support PCI P2P. Logan _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme