Re: [PATCH v7 01/21] lib/scatterlist: add flag for indicating P2PDMA segments in an SGL

Christoph Hellwig
2022-06-29T06:33:18Z

On Wed, Jun 15, 2022 at 10:12:13AM -0600, Logan Gunthorpe wrote:
> Make use of the third free LSB in scatterlist's page_link on 64bit systems.
>
> The extra bit will be used by dma_[un]map_sg_p2pdma() to determine when a
> given SGL segments dma_address points to a PCI bus address.
> dma_unmap_sg_p2pdma() will need to perform different cleanup when a
> segment is marked as a bus address.
>
> The new bit will only be used when CONFIG_PCI_P2PDMA is set; this means
> PCI P2PDMA will require CONFIG_64BIT. This should be acceptable as the
> majority of P2PDMA use cases are restricted to newer root complexes and
> roughly require the extra address space for memory BARs used in the
> transactions.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>