From mboxrd@z Thu Jan  1 00:00:00 1970
From: Logan Gunthorpe <logang-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
Subject: Re: [PATCH 06/12] IB/core: Add optional PCI P2P flag to
 rdma_rw_ctx_[init|destroy]()
Date: Mon, 8 Jan 2018 12:05:57 -0700
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To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, Keith Busch <keith.busch-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>, Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Max Gurtovoy <maxg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
List-Id: linux-rdma@vger.kernel.org



On 08/01/18 11:57 AM, Christoph Hellwig wrote:
> It does, sort of - but in a different way then the normal DMA map
> ops.  And only to work around the fact that we need to map our
> P2P space into struct pages.  Without that we could just pass the
> bus address around, but the Linux stack and VM isn't anywhere near
> ready for something that advanced.

Yeah, wouldn't that be nice.

Ok, so if we shouldn't touch the dma_map infrastructure how should the 
workaround to opt-out HFI and QIB look? I'm not that familiar with the 
RDMA code.

Thanks,

Logan