lkml.org 
[lkml]   [2018]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 3/5] dma-direct: refine dma_direct_alloc zone selection
    From
    Date
    On 20/09/18 19:52, Christoph Hellwig wrote:
    > We need to take the DMA offset and encryption bit into account when
    > selecting a zone. User the opportunity to factor out the zone
    > selection into a helper for reuse.
    >
    > Signed-off-by: Christoph Hellwig <hch@lst.de>
    > ---
    > kernel/dma/direct.c | 31 +++++++++++++++++++++----------
    > 1 file changed, 21 insertions(+), 10 deletions(-)
    >
    > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
    > index 81b73a5bba54..3c404e33d946 100644
    > --- a/kernel/dma/direct.c
    > +++ b/kernel/dma/direct.c
    > @@ -68,6 +68,22 @@ u64 dma_direct_get_required_mask(struct device *dev)
    > return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
    > }
    >
    > +static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
    > + u64 *phys_mask)
    > +{
    > + if (force_dma_unencrypted())
    > + *phys_mask = __dma_to_phys(dev, dma_mask);
    > + else
    > + *phys_mask = dma_to_phys(dev, dma_mask);

    Maybe make phys_to_dma_direct() take u64 instead of phys_addr_t so we
    can reuse it here?

    > + /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
    > + if (*phys_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
    > + return GFP_DMA;

    If we don't have ZONE_DMA it would in theory be a tiny bit better to
    fall back to GFP_DMA32 instead of returning 0 here, but I'm not sure
    it's worth the bother.

    > + if (*phys_mask <= DMA_BIT_MASK(32))
    > + return GFP_DMA32;
    > + return 0;
    > +}
    > +
    > static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
    > {
    > return phys_to_dma_direct(dev, phys) + size - 1 <=
    > @@ -80,17 +96,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
    > unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
    > int page_order = get_order(size);
    > struct page *page = NULL;
    > + u64 phys_mask;
    > void *ret;
    >
    > /* we always manually zero the memory once we are done: */
    > gfp &= ~__GFP_ZERO;
    > -
    > - /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
    > - if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
    > - gfp |= GFP_DMA;
    > - if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
    > - gfp |= GFP_DMA32;
    > -
    > + gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
    > + &phys_mask);
    > again:
    > /* CMA can be used only in the context which permits sleeping */
    > if (gfpflags_allow_blocking(gfp)) {
    > @@ -109,15 +121,14 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
    > page = NULL;
    >
    > if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
    > - dev->coherent_dma_mask < DMA_BIT_MASK(64) &&
    > + phys_mask < DMA_BIT_MASK(64) &&
    > !(gfp & (GFP_DMA32 | GFP_DMA))) {
    > gfp |= GFP_DMA32;
    > goto again;

    Ah right, in that situation we should probably end up here anyway, so
    that's good enough - definitely not worth any more #ifdeffery above.
    Nits aside,

    Reviewed-by: Robin Murphy <robin.murphy@arm.com>

    > }
    >
    > if (IS_ENABLED(CONFIG_ZONE_DMA) &&
    > - dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
    > - !(gfp & GFP_DMA)) {
    > + phys_mask < DMA_BIT_MASK(32) && !(gfp & GFP_DMA)) {
    > gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
    > goto again;
    > }
    >

    \
     
     \ /
      Last update: 2018-09-27 16:31    [W:3.785 / U:0.752 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site