lkml.org 
[lkml]   [2019]   [Jul]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: use exact allocation for dma coherent memory
    From
    Date


    On 7/1/2019 10:48 AM, Christoph Hellwig wrote:
    > On Fri, Jun 14, 2019 at 03:47:10PM +0200, Christoph Hellwig wrote:
    >> Switching to a slightly cleaned up alloc_pages_exact is pretty easy,
    >> but it turns out that because we didn't filter valid gfp_t flags
    >> on the DMA allocator, a bunch of drivers were passing __GFP_COMP
    >> to it, which is rather bogus in too many ways to explain. Arm has
    >> been filtering it for a while, but this series instead tries to fix
    >> the drivers and warn when __GFP_COMP is passed, which makes it much
    >> larger than just adding the functionality.
    >
    > Dear driver maintainers,
    >
    > can you look over the patches touching your drivers, please? I'd
    > like to get as much as possible of the driver patches into this
    > merge window, so that it can you through your maintainer trees.

    You made me look ;-) Actually not touching my drivers so I'm off the
    hook. However, I was wondering if drivers could know so I decided to
    look into the DMA-API.txt documentation which currently states:

    """
    The flag parameter (dma_alloc_coherent() only) allows the caller to
    specify the ``GFP_`` flags (see kmalloc()) for the allocation (the
    implementation may choose to ignore flags that affect the location of
    the returned memory, like GFP_DMA).
    """

    I do expect you are going to change that description as well now that
    you are going to issue a warning on __GFP_COMP. Maybe include that in
    patch 15/16 where you introduce that warning.

    Regards,
    Arend

    \
     
     \ /
      Last update: 2019-07-02 11:49    [W:4.065 / U:0.084 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site