To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Matthew Wilcox <willy@infradead.org>, linux-kernel@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>,
        Joao Martins <joao.m.martins@oracle.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org,
        netdev@vger.kernel.org, linux-mm@kvack.org,
        linux-rdma@vger.kernel.org, dri-devel@lists.freedesktop.org,
        nvdimm@lists.linux.dev
References: <YdyKWeU0HTv8m7wD@casper.infradead.org>
 <20220111004126.GJ2328285@nvidia.com> <Yd0IeK5s/E0fuWqn@casper.infradead.org>
 <20220111150142.GL2328285@nvidia.com> <Yd3Nle3YN063ZFVY@casper.infradead.org>
 <20220111202159.GO2328285@nvidia.com> <Yd311C45gpQ3LqaW@casper.infradead.org>
 <ef01ce7d-f1d3-0bbb-38ba-2de4d3f7e31a@deltatee.com>
 <20220111225713.GS2328285@nvidia.com>
From:   Logan Gunthorpe <logang@deltatee.com>
Message-ID: <ee523bd5-2818-269b-8b94-89106ad41767@deltatee.com>
Date:   Tue, 11 Jan 2022 16:02:44 -0700
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Subject: Re: Phyr Starter
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On 2022-01-11 3:57 p.m., Jason Gunthorpe wrote:
> On Tue, Jan 11, 2022 at 03:09:13PM -0700, Logan Gunthorpe wrote:
> 
>> Either that, or we need a wrapper that allocates an appropriately
>> sized SGL to pass to any dma_map implementation that doesn't support
>> the new structures.
> 
> This is what I think we should do. If we start with RDMA then we can
> motivate the 4 main server IOMMU drivers to get updated ASAP, then it
> can acceptably start to spread to other users.

I suspect the preferred path forward is for the IOMMU drivers that don't
use dma-iommu should be converted to use it. Then anything we do to
dma-iommu will be applicable to the IOMMU drivers. Better than expecting
them to implement a bunch of new functionality themselves.

Logan