From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
Chaitanya Kulkarni <kch@nvidia.com>,
Kanchan Joshi <joshi.k@samsung.com>,
Leon Romanovsky <leon@kernel.org>,
Nitesh Shetty <nj.shetty@samsung.com>,
Logan Gunthorpe <logang@deltatee.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
Leon Romanovsky <leonro@nvidia.com>
Subject: Re: [PATCH 2/8] block: add scatterlist-less DMA mapping helpers
Date: Mon, 23 Jun 2025 09:43:20 -0600 [thread overview]
Message-ID: <aFl2GJskYNdvZDDo@kbusch-mbp> (raw)
In-Reply-To: <20250623141259.76767-3-hch@lst.de>
On Mon, Jun 23, 2025 at 04:12:24PM +0200, Christoph Hellwig wrote:
> Add a new blk_rq_dma_map / blk_rq_dma_unmap pair that does away with
> the wasteful scatterlist structure. Instead it uses the mapping iterator
> to either add segments to the IOVA for IOMMU operations, or just maps
> them one by one for the direct mapping. For the IOMMU case instead of
> a scatterlist with an entry for each segment, only a single [dma_addr,len]
> pair needs to be stored for processing a request, and for the direct
> mapping the per-segment allocation shrinks from
> [page,offset,len,dma_addr,dma_len] to just [dma_addr,len].
>
> One big difference to the scatterlist API, which could be considered
> downside, is that the IOVA collapsing only works when the driver sets
> a virt_boundary that matches the IOMMU granule. For NVMe this is done
> already so it works perfectly.
Looks good.
Reviewed-by: Keith Busch <kbusch@kernel.org>
next prev parent reply other threads:[~2025-06-23 15:43 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-23 14:12 new DMA API conversion for nvme-pci v2 Christoph Hellwig
2025-06-23 14:12 ` [PATCH 1/8] block: don't merge different kinds of P2P transfers in a single bio Christoph Hellwig
2025-06-23 15:43 ` Keith Busch
2025-06-23 14:12 ` [PATCH 2/8] block: add scatterlist-less DMA mapping helpers Christoph Hellwig
2025-06-23 15:43 ` Keith Busch [this message]
2025-06-23 14:12 ` [PATCH 3/8] nvme-pci: refactor nvme_pci_use_sgls Christoph Hellwig
2025-06-23 15:27 ` Keith Busch
2025-06-24 12:46 ` Christoph Hellwig
2025-06-25 4:28 ` Chaitanya Kulkarni
2025-06-25 6:07 ` Christoph Hellwig
2025-06-23 14:12 ` [PATCH 4/8] nvme-pci: merge the simple PRP and SGL setup into a common helper Christoph Hellwig
2025-06-23 15:43 ` Keith Busch
2025-06-23 14:12 ` [PATCH 5/8] nvme-pci: remove superfluous arguments Christoph Hellwig
2025-06-23 14:12 ` [PATCH 6/8] nvme-pci: convert the data mapping to blk_rq_dma_map Christoph Hellwig
2025-06-23 15:44 ` Keith Busch
2025-06-23 14:12 ` [PATCH 7/8] nvme-pci: replace NVME_MAX_KB_SZ with NVME_MAX_BYTE Christoph Hellwig
2025-06-23 15:44 ` Keith Busch
2025-06-23 14:12 ` [PATCH 8/8] nvme-pci: rework the build time assert for NVME_MAX_NR_DESCRIPTORS Christoph Hellwig
2025-06-23 15:44 ` Keith Busch
2025-06-23 21:45 ` new DMA API conversion for nvme-pci v2 Chaitanya Kulkarni
2025-06-25 4:32 ` Chaitanya Kulkarni
-- strict thread matches above, loose matches on Subject: below --
2025-06-25 11:34 new DMA API conversion for nvme-pci v3 Christoph Hellwig
2025-06-25 11:34 ` [PATCH 2/8] block: add scatterlist-less DMA mapping helpers Christoph Hellwig
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