lkml.org 
[lkml]   [2020]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH] dma-pool: use single atomic pool for both DMA zones
    From
    Date
    On 2020-07-08 16:36, Christoph Hellwig wrote:
    > On Wed, Jul 08, 2020 at 12:35:34PM +0200, Nicolas Saenz Julienne wrote:
    >>> Which allows me to switch between ACPI/DT on the machine. In DT mode it
    >>> works fine now,
    >>
    >> Nice, would that count as a Tested-by from you?
    >>
    >>> but with ACPI I continue to have failures unless I
    >>> disable CMA via cma=0 on the kernel command line.
    >>
    >> Yes, I see why, in atomic_pool_expand() memory is allocated from CMA without
    >> checking its correctness. That calls for a separate fix. I'll try to think of
    >> something.
    >
    > I think we need a dma_coherent_ok for the allocations from the
    > pool and then fall back to the next better one to get started. And
    > yes, CMA is a bit of a mess, that generally needs better checks.

    Yeah, another thought that came to mind later is that iommu-dma can use
    pages from any pool regardless of the device's DMA mask, so we could
    stand to be a lot less restrictive in that case too.

    Perhaps it is better to just bite the bullet, keep the straightforward
    one-pool-per-zone setup, and implement the dma_coherent_ok() type
    fallback logic. More complexity for dma_alloc_from_pool(), but
    everything else stays nice and simple - lose the assumption that
    dev_to_pool() can work for this and and just let callers pass an
    allocation mask directly, and have dma_free_from_pool() simply check all
    available pools.

    Robin.

    \
     
     \ /
      Last update: 2020-07-08 18:20    [W:5.824 / U:0.300 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site