Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
To:     Sinan Kaya <okaya@codeaurora.org>, 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
Cc:     Stephen Bates <sbates@raithlin.com>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Keith Busch <keith.busch@intel.com>,
        Sagi Grimberg <sagi@grimberg.me>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Max Gurtovoy <maxg@mellanox.com>,
        Dan Williams <dan.j.williams@intel.com>,
        =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Alex Williamson <alex.williamson@redhat.com>
References: <20180312193525.2855-1-logang@deltatee.com>
 <20180312193525.2855-2-logang@deltatee.com>
 <59fd2f5d-177f-334a-a9c4-0f8a6ec7c303@codeaurora.org>
 <24d8e5c2-065d-8bde-3f5d-7f158be9c578@deltatee.com>
 <52cbbbc4-c488-f83f-8d02-14d455b4efd7@codeaurora.org>
 <3e738f95-d73c-4182-2fa1-8664aafb1ab7@deltatee.com>
 <703aa92c-0c1c-4852-5887-6f6e6ccde0fb@codeaurora.org>
 <a0af83f8-2cbc-862b-6f8b-231991527cfc@deltatee.com>
 <3ea80992-a0fc-08f2-d93d-ae0ec4e3f4ce@codeaurora.org>
From:   Logan Gunthorpe <logang@deltatee.com>
Message-ID: <4eb6850c-df1b-fd44-3ee0-d43a50270b53@deltatee.com>
Date:   Tue, 13 Mar 2018 14:46:31 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.6.0
MIME-Version: 1.0
In-Reply-To: <3ea80992-a0fc-08f2-d93d-ae0ec4e3f4ce@codeaurora.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Subject: Re: [PATCH v3 01/11] PCI/P2PDMA: Support peer-to-peer memory
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 13/03/18 01:53 PM, Sinan Kaya wrote:
> I agree disabling globally would be bad. Somebody can always say I have
> ten switches on my system. I want to do peer-to-peer on one switch only. Now,
> this change weakened security for the other switches that I had no intention
> with doing P2P.
> 
> Isn't this a problem?

Well, if it's a problem for someone they'll have to solve it. We're
targeting JBOFs that have no use for ACS / IOMMU groups at all.

> Can we specify the BDF of the downstream device we want P2P with during boot via
> kernel command line?

That's a painful configuration burden. And then things might stop
working if you change your topology at all and now have to change boot
parameters.

Logan