From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org,
linux-rdma@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>,
Bjorn Helgaas <bhelgaas@google.com>,
Dan Williams <dan.j.williams@intel.com>,
Sagi Grimberg <sagi@grimberg.me>, Keith Busch <kbusch@kernel.org>,
Stephen Bates <sbates@raithlin.com>
Subject: Re: [RFC PATCH 20/28] IB/core: Introduce API for initializing a RW ctx from a DMA address
Date: Thu, 20 Jun 2019 10:59:44 -0600 [thread overview]
Message-ID: <f9186b2b-7737-965f-2dca-25e40e566e64@deltatee.com> (raw)
In-Reply-To: <20190620164909.GC19891@ziepe.ca>
On 2019-06-20 10:49 a.m., Jason Gunthorpe wrote:
> On Thu, Jun 20, 2019 at 10:12:32AM -0600, Logan Gunthorpe wrote:
>> Introduce rdma_rw_ctx_dma_init() and rdma_rw_ctx_dma_destroy() which
>> peform the same operation as rdma_rw_ctx_init() and
>> rdma_rw_ctx_destroy() respectively except they operate on a DMA
>> address and length instead of an SGL.
>>
>> This will be used for struct page-less P2PDMA, but there's also
>> been opinions expressed to migrate away from SGLs and struct
>> pages in the RDMA APIs and this will likely fit with that
>> effort.
>>
>> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
>> drivers/infiniband/core/rw.c | 74 ++++++++++++++++++++++++++++++------
>> include/rdma/rw.h | 6 +++
>> 2 files changed, 69 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/infiniband/core/rw.c b/drivers/infiniband/core/rw.c
>> index 32ca8429eaae..cefa6b930bc8 100644
>> +++ b/drivers/infiniband/core/rw.c
>> @@ -319,6 +319,39 @@ int rdma_rw_ctx_init(struct rdma_rw_ctx *ctx, struct ib_qp *qp, u8 port_num,
>> }
>> EXPORT_SYMBOL(rdma_rw_ctx_init);
>>
>> +/**
>> + * rdma_rw_ctx_dma_init - initialize a RDMA READ/WRITE context from a
>> + * DMA address instead of SGL
>> + * @ctx: context to initialize
>> + * @qp: queue pair to operate on
>> + * @port_num: port num to which the connection is bound
>> + * @addr: DMA address to READ/WRITE from/to
>> + * @len: length of memory to operate on
>> + * @remote_addr:remote address to read/write (relative to @rkey)
>> + * @rkey: remote key to operate on
>> + * @dir: %DMA_TO_DEVICE for RDMA WRITE, %DMA_FROM_DEVICE for RDMA READ
>> + *
>> + * Returns the number of WQEs that will be needed on the workqueue if
>> + * successful, or a negative error code.
>> + */
>> +int rdma_rw_ctx_dma_init(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
>> + u8 port_num, dma_addr_t addr, u32 len, u64 remote_addr,
>> + u32 rkey, enum dma_data_direction dir)
>
> Why not keep the same basic signature here but replace the scatterlist
> with the dma vec ?
Could do. At the moment, I had no need for dma_vec in this interface.
>> +{
>> + struct scatterlist sg;
>> +
>> + sg_dma_address(&sg) = addr;
>> + sg_dma_len(&sg) = len;
>
> This needs to fail if the driver is one of the few that require
> struct page to work..
Yes, right. Currently P2PDMA checks for the use of dma_virt_ops. And
that probably should also be done here. But is that sufficient? You're
probably right that it'll take an audit of the RDMA tree to sort that out.
> Really want I want to do is to have this new 'dma vec' pushed through
> the RDMA APIs so we know that if a driver is using the dma vec
> interface it is struct page free.
Yeah, I know you were talking about heading this way during LSF/MM and
is partly what inspired this series. However, largely, my focus for this
RFC was the block layer to see this is an acceptable approach -- I just
kind of hacked RDMA for now.
> This is not so hard to do, as most drivers are already struct page
> free, but is pretty much blocked on needing some way to go from the
> block layer SGL world to the dma vec world that does not hurt storage
> performance.
Maybe I can end up helping with that if it helps push the ideas here
through. (And assuming people think it's an acceptable approach for the
block-layer side of things).
Thanks,
Logan
next prev parent reply other threads:[~2019-06-20 16:59 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 16:12 [RFC PATCH 00/28] Removing struct page from P2PDMA Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 01/28] block: Introduce DMA direct request type Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 02/28] block: Add dma_vec structure Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 03/28] block: Warn on mis-use of dma-direct bios Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 04/28] block: Never bounce " Logan Gunthorpe
2019-06-20 17:23 ` Jason Gunthorpe
2019-06-20 18:38 ` Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 05/28] block: Skip dma-direct bios in bio_integrity_prep() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 06/28] block: Support dma-direct bios in bio_advance_iter() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 07/28] block: Use dma_vec length in bio_cur_bytes() for dma-direct bios Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 08/28] block: Introduce dmavec_phys_mergeable() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 09/28] block: Introduce vec_gap_to_prev() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 10/28] block: Create generic vec_split_segs() from bvec_split_segs() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 11/28] block: Create blk_segment_split_ctx Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 12/28] block: Create helper for bvec_should_split() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 13/28] block: Generalize bvec_should_split() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 14/28] block: Support splitting dma-direct bios Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 15/28] block: Support counting dma-direct bio segments Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 16/28] block: Implement mapping dma-direct requests to SGs in blk_rq_map_sg() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 17/28] block: Introduce queue flag to indicate support for dma-direct bios Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 18/28] block: Introduce bio_add_dma_addr() Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 19/28] nvme-pci: Support dma-direct bios Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 20/28] IB/core: Introduce API for initializing a RW ctx from a DMA address Logan Gunthorpe
2019-06-20 16:49 ` Jason Gunthorpe
2019-06-20 16:59 ` Logan Gunthorpe [this message]
2019-06-20 17:11 ` Jason Gunthorpe
2019-06-20 18:24 ` Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 21/28] nvmet: Split nvmet_bdev_execute_rw() into a helper function Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 22/28] nvmet: Use DMA addresses instead of struct pages for P2P Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 23/28] nvme-pci: Remove support for PCI_P2PDMA requests Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 24/28] block: Remove PCI_P2PDMA queue flag Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 25/28] IB/core: Remove P2PDMA mapping support in rdma_rw_ctx Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 26/28] PCI/P2PDMA: Remove SGL helpers Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 27/28] PCI/P2PDMA: Remove struct pages that back P2PDMA memory Logan Gunthorpe
2019-06-20 16:12 ` [RFC PATCH 28/28] memremap: Remove PCI P2PDMA page memory type Logan Gunthorpe
2019-06-20 18:45 ` [RFC PATCH 00/28] Removing struct page from P2PDMA Dan Williams
2019-06-20 19:33 ` Jason Gunthorpe
2019-06-20 20:18 ` Dan Williams
2019-06-20 20:51 ` Logan Gunthorpe
2019-06-21 17:47 ` Jason Gunthorpe
2019-06-21 17:54 ` Dan Williams
2019-06-24 7:31 ` Christoph Hellwig
2019-06-24 13:46 ` Jason Gunthorpe
2019-06-24 13:50 ` Christoph Hellwig
2019-06-24 13:55 ` Jason Gunthorpe
2019-06-24 16:53 ` Logan Gunthorpe
2019-06-24 18:16 ` Jason Gunthorpe
2019-06-24 18:28 ` Logan Gunthorpe
2019-06-24 18:54 ` Jason Gunthorpe
2019-06-24 19:37 ` Logan Gunthorpe
2019-06-24 16:10 ` Logan Gunthorpe
2019-06-25 7:18 ` Christoph Hellwig
2019-06-20 19:34 ` Logan Gunthorpe
2019-06-20 23:40 ` Dan Williams
2019-06-20 23:42 ` Logan Gunthorpe
2019-06-24 7:27 ` Christoph Hellwig
2019-06-24 16:07 ` Logan Gunthorpe
2019-06-25 7:20 ` Christoph Hellwig
2019-06-25 15:57 ` Logan Gunthorpe
2019-06-25 17:01 ` Christoph Hellwig
2019-06-25 19:54 ` Logan Gunthorpe
2019-06-26 6:57 ` Christoph Hellwig
2019-06-26 18:31 ` Logan Gunthorpe
2019-06-26 20:21 ` Jason Gunthorpe
2019-06-26 20:39 ` Dan Williams
2019-06-26 20:54 ` Jason Gunthorpe
2019-06-26 20:55 ` Logan Gunthorpe
2019-06-26 20:45 ` Logan Gunthorpe
2019-06-26 21:00 ` Jason Gunthorpe
2019-06-26 21:18 ` Logan Gunthorpe
2019-06-27 6:32 ` Jason Gunthorpe
2019-06-27 16:09 ` Logan Gunthorpe
2019-06-27 16:35 ` Jason Gunthorpe
2019-06-27 16:49 ` Logan Gunthorpe
2019-06-28 4:57 ` Jason Gunthorpe
2019-06-28 16:22 ` Logan Gunthorpe
2019-06-28 17:29 ` Jason Gunthorpe
2019-06-28 18:29 ` Logan Gunthorpe
2019-06-28 19:09 ` Jason Gunthorpe
2019-06-28 19:35 ` Logan Gunthorpe
2019-07-02 22:45 ` Jason Gunthorpe
2019-07-02 22:52 ` Logan Gunthorpe
2019-06-27 9:08 ` Christoph Hellwig
2019-06-27 16:30 ` Logan Gunthorpe
2019-06-27 17:00 ` Christoph Hellwig
2019-06-27 18:00 ` Logan Gunthorpe
2019-06-28 13:38 ` Christoph Hellwig
2019-06-28 15:54 ` Logan Gunthorpe
2019-06-27 9:01 ` Christoph Hellwig
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