lkml.org 
[lkml]   [2013]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not enough ram for it
    On Tue, Jan 08, 2013 at 03:40:11PM -0800, Yinghai Lu wrote:
    > On Mon, Jan 7, 2013 at 7:50 PM, Yinghai Lu <yinghai@kernel.org> wrote:
    > > On Mon, Jan 7, 2013 at 7:13 PM, Eric W. Biederman <ebiederm@xmission.com> wrote:
    > >> I meant we should detect failure to allocate bounce buffers in in
    > >> swiotlb_init() instead of panicing.
    > >>
    > >> I meant swiotlb_map_single() should either panic or simply fail.
    > >>
    > >> If I have read lib/swiotlb.c correctly the only place we allocate a
    > >> bounce buffer is in swiotlb_map_single. If there are more places we can
    > >> allocate bounce buffers those need to be handled as well.
    > >
    > > ok, will give it a try.
    >
    > please check if you are ok with attached.
    >
    > looks like it need more change of lines.

    The swiotlb_full check I don't believe is neccessary. You won't ever get
    to that unless swiotlb_map_page has at least provided a bounce buffer.
    And if the swiotlb_map_page does not have a bounce buffer it will exit
    with:

    + if (no_iotlb_memory)
    + return SWIOTLB_MAP_ERROR;
    +

    which is dangerous. That is b/c there are drivers that don't use the
    dma_mapping_error check (so check the bus address after calling
    pci_map_*). This means they would try to do DMA on 0xffffffff (yikes!).

    That is reason the failback (v_overflow_buffer) is still in
    usage - b/c we have drivers that might just do this and this is the last
    resort for them. And until those drivers are fixed - we _need_ this
    fallback to work.


    \
     
     \ /
      Last update: 2013-01-09 02:21    [W:3.594 / U:0.280 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site