From: Robin Murphy <robin.murphy@arm.com>
To: Christoph Hellwig <hch@lst.de>, Logan Gunthorpe <logang@deltatee.com>
Cc: "Matthew Wilcox" <willy@infradead.org>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
linux-pci@vger.kernel.org,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Ira Weiny" <iweiny@intel.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
"Stephen Bates" <sbates@raithlin.com>,
linux-block@vger.kernel.org, linux-mm@kvack.org,
iommu@lists.linux-foundation.org,
"Christian König" <christian.koenig@amd.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Dan Williams" <dan.j.williams@intel.com>
Subject: Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL
Date: Mon, 9 Nov 2020 14:02:21 +0000 [thread overview]
Message-ID: <491c26de-bda0-3266-a67d-ee2580559a54@arm.com> (raw)
In-Reply-To: <20201109091258.GB28918@lst.de>
On 2020-11-09 09:12, Christoph Hellwig wrote:
> On Fri, Nov 06, 2020 at 10:00:25AM -0700, Logan Gunthorpe wrote:
>> We make use of the top bit of the dma_length to indicate a P2PDMA
>> segment.
>
> I don't think "we" can. There is nothing limiting the size of a SGL
> segment.
Right, the story behind ab2cbeb0ed30 ("iommu/dma: Handle SG length
overflow better") comes immediately to mind, for one. If all the P2P
users can agree to be in on the game then by all means implement this in
the P2P code, but I don't think it belongs in the generic top-level
scatterlist API.
Robin.
next prev parent reply other threads:[~2020-11-09 14:02 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 17:00 [RFC PATCH 00/15] Userspace P2PDMA with O_DIRECT NVMe devices Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 01/15] PCI/P2PDMA: Don't sleep in upstream_bridge_distance_warn() Logan Gunthorpe
2020-11-09 9:12 ` Christoph Hellwig
2020-11-06 17:00 ` [RFC PATCH 02/15] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset() Logan Gunthorpe
2020-11-10 23:25 ` Bjorn Helgaas
2020-11-10 23:42 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2020-11-09 9:12 ` Christoph Hellwig
2020-11-09 14:02 ` Robin Murphy [this message]
2020-11-09 16:47 ` Logan Gunthorpe
2020-12-10 1:22 ` Dan Williams
2020-12-10 2:06 ` Logan Gunthorpe
2020-12-10 4:04 ` Dan Williams
2020-12-10 16:44 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 05/15] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 06/15] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 07/15] iommu/dma: Support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 08/15] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 09/15] nvme-pci: Convert to using dma_map_sg for p2pdma pages Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 10/15] mm: Introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 11/15] iov_iter: Introduce iov_iter_get_pages_[alloc_]flags() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 12/15] block: Set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 13/15] block: Set FOLL_PCI_P2PDMA in bio_map_user_iov() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 14/15] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Logan Gunthorpe
2020-11-06 17:22 ` Jason Gunthorpe
2020-11-06 17:28 ` Logan Gunthorpe
2020-11-06 17:42 ` Jason Gunthorpe
2020-11-06 17:53 ` Logan Gunthorpe
2020-11-06 18:09 ` Jason Gunthorpe
2020-11-06 18:20 ` Logan Gunthorpe
2020-11-06 19:30 ` Jason Gunthorpe
2020-11-06 19:44 ` Logan Gunthorpe
2020-11-06 19:53 ` Jason Gunthorpe
2020-11-06 20:03 ` Logan Gunthorpe
2020-11-07 0:14 ` Jason Gunthorpe
2020-11-07 2:50 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 15/15] nvme-pci: Allow mmaping the CMB in userspace Logan Gunthorpe
2020-11-06 17:39 ` Jason Gunthorpe
2020-11-06 17:43 ` Logan Gunthorpe
2020-11-09 15:03 ` Keith Busch
2020-11-09 16:50 ` Logan Gunthorpe
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