From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Date: Wed, 19 Apr 2017 09:55:57 -0600 Message-ID: <20170419155557.GA8497@obsidianresearch.com> References: <1492381396.25766.43.camel@kernel.crashing.org> <20170418164557.GA7181@obsidianresearch.com> <20170418190138.GH7181@obsidianresearch.com> <20170418210339.GA24257@obsidianresearch.com> <1492564806.25766.124.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1492564806.25766.124.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Benjamin Herrenschmidt Cc: Dan Williams , Logan Gunthorpe , Bjorn Helgaas , Christoph Hellwig , Sagi Grimberg , "James E.J. Bottomley" , "Martin K. Petersen" , Jens Axboe , Steve Wise , Stephen Bates , Max Gurtovoy , Keith Busch , linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-scsi , linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvdimm , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Jerome Glisse List-Id: linux-rdma@vger.kernel.org On Wed, Apr 19, 2017 at 11:20:06AM +1000, Benjamin Herrenschmidt wrote: > That helper wouldn't perform the actual iommu mapping. It would simply > return something along the lines of: > > - "use that alternate bus address and don't map in the iommu" I was thinking only this one would be supported with a core code helper.. > - "use that alternate bus address and do map in the iommu" > - "proceed as normal" .. because I don't have an idea how a core code helper could figure out what the platform needs for the above two .. I think many of the iommu platforms will need to construct their own bus address in the iommu, and we already have easy access to the CPU address. Presumably once a transcation passes through the iommu it needs to be using the CPU address for the target bar, otherwise things are going to be ambiguous.. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html