Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 29 Jul 2019 11:57:19 +0200 | Subject | Re: [PATCH 4/5] dma-mapping: provide a better default ->get_required_mask |
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Hi Christoph,
On Thu, Jul 25, 2019 at 8:35 AM Christoph Hellwig <hch@lst.de> wrote: > Most dma_map_ops instances are IOMMUs that work perfectly fine in 32-bits > of IOVA space, and the generic direct mapping code already provides its > own routines that is intelligent based on the amount of memory actually > present. Wire up the dma-direct routine for the ARM direct mapping code > as well, and otherwise default to the constant 32-bit mask. This way > we only need to override it for the occasional odd IOMMU that requires > 64-bit IOVA support, or IOMMU drivers that are more efficient if they > can fall back to the direct mapping.
As I know you like diving into cans of worms ;-)
Does 64-bit IOVA support actually work in general? Or only on 64-bit platforms, due to dma_addr_t to unsigned long truncation on 32-bit?
https://lore.kernel.org/linux-renesas-soc/CAMuHMdWkQ918Y61tMJbHEu29AGLEyNwbvZbSBB-RRH7YYUNRcA@mail.gmail.com/
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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