On 2020-12-09 6:22 p.m., Dan Williams wrote: > On Mon, Nov 9, 2020 at 8:47 AM Logan Gunthorpe <log...@deltatee.com> wrote: >> >> >> >> On 2020-11-09 2:12 a.m., 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. >> >> Yes, I expected this would be the unacceptable part. Any alternative ideas? > > Why is the SG_P2PDMA_FLAG needed as compared to checking the SGL > segment-pages for is_pci_p2pdma_page()? Because the DMA and page segments in the SGL aren't necessarily aligned... The IOMMU implementations can coalesce multiple pages into fewer DMA address ranges, so the page pointed to by sg->page_link may not be the one that corresponds to the address in sg->dma_address for a given segment. If that makes sense -- it's not the easiest thing to explain. Logan _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
- Re: [RFC PATCH 14/15] PCI/P2PD... Jason Gunthorpe
- Re: [RFC PATCH 14/15] PCI/P2PD... Logan Gunthorpe
- [RFC PATCH 13/15] block: Set FOLL_PCI_P2PDMA in bio_map_... Logan Gunthorpe
- [RFC PATCH 11/15] iov_iter: Introduce iov_iter_get_pages... Logan Gunthorpe
- [RFC PATCH 12/15] block: Set FOLL_PCI_P2PDMA in __bio_io... Logan Gunthorpe
- [RFC PATCH 04/15] lib/scatterlist: Add flag for indicati... Logan Gunthorpe
- Re: [RFC PATCH 04/15] lib/scatterlist: Add flag for... Christoph Hellwig
- Re: [RFC PATCH 04/15] lib/scatterlist: Add flag... Robin Murphy
- Re: [RFC PATCH 04/15] lib/scatterlist: Add flag... Logan Gunthorpe
- Re: [RFC PATCH 04/15] lib/scatterlist: Add ... Dan Williams
- Re: [RFC PATCH 04/15] lib/scatterlist: ... Logan Gunthorpe
- Re: [RFC PATCH 04/15] lib/scatterl... Dan Williams
- Re: [RFC PATCH 04/15] lib/scat... Logan Gunthorpe
- [RFC PATCH 06/15] dma-mapping: Add flags to dma_map_ops ... Logan Gunthorpe
- [RFC PATCH 07/15] iommu/dma: Support PCI P2PDMA pages in... Logan Gunthorpe
- [RFC PATCH 02/15] PCI/P2PDMA: Attempt to set map_type if... Logan Gunthorpe
- [RFC PATCH 09/15] nvme-pci: Convert to using dma_map_sg ... Logan Gunthorpe
- [RFC PATCH 05/15] dma-direct: Support PCI P2PDMA pages i... Logan Gunthorpe
- [RFC PATCH 15/15] nvme-pci: Allow mmaping the CMB in use... Logan Gunthorpe
- Re: [RFC PATCH 15/15] nvme-pci: Allow mmaping the C... Jason Gunthorpe
- Re: [RFC PATCH 15/15] nvme-pci: Allow mmaping t... Logan Gunthorpe