[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v6 12/19] swiotlb: don't assume that io_tlb_start-io_tlb_end is coherent
On Wed, Oct 02, 2013 at 06:31:57PM +0100, Stefano Stabellini wrote: > On Mon, 30 Sep 2013, Konrad Rzeszutek Wilk wrote: > > On Fri, Sep 27, 2013 at 05:10:00PM +0100, Stefano Stabellini wrote: > > > The swiotlb code has appropriate calls to dma_mark_clean in place for > > > buffers passed to swiotlb_map_page as an argument. However it assumes > > > that the swiotlb bounce buffer (io_tlb_start-io_tlb_end) is already > > > coherent and doesn't need any calls to dma_mark_clean. > > > > > > On ARM the swiotlb bounce buffer is not coherent (the memory is > > > writealloc while it should be bufferable) and therefore we need to call > > > dma_mark_clean appropriately on the bounce buffer code paths too. > > > > > > Note that most architecures have an empty dma_mark_clean implementation > > > anyway. > > > > The other architecture that uses swiotlb is IA64 and that does have > > an implementation where it touches on page attributes. > > > > Which means I have to figure out why my HP zx6000 won't boot with 3.11 now > > :-( > > > > Now this is a very thorny issue. > > Honestly I don't like the dma_mark_clean interface very much: it's one > big hammer, when we actually need some finesse to handle coherency. > > For example on ARM some devices might not need the dma_mark_clean call, > while others do. Calling it all the times is at the very best > inefficient and incorrect at worst. > > I am thinking of calling the original map/unmap_page functions instead > (arm_dma_map_page or arm_coherent_dma_map_page in the arm case). > However in order to do that I would need to add more __get_dma_ops calls in > both lib/swiotlb.c and drivers/xen/swiotlb-xen.c I think that is OK for the Xen-SWIOTLB case. For the lib/swiotlb - would that mean that non-Xen-ARM would use the SWIOTLB? If so, I am OK with that too. > > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> > > > --- > > > lib/swiotlb.c | 13 ++++++++++--- > > > 1 files changed, 10 insertions(+), 3 deletions(-) > > > > > > diff --git a/lib/swiotlb.c b/lib/swiotlb.c > > > index 4e8686c..eb45d17 100644 > > > --- a/lib/swiotlb.c > > > +++ b/lib/swiotlb.c > > > @@ -515,6 +515,7 @@ found: > > > io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT); > > > if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) > > > swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE); > > > + dma_mark_clean(phys_to_virt(tlb_addr), size); > > > > > > return tlb_addr; > > > } > > > @@ -547,7 +548,10 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, > > > phys_addr_t tlb_addr, > > > * First, sync the memory before unmapping the entry > > > */ > > > if (orig_addr && ((dir == DMA_FROM_DEVICE) || (dir == > > > DMA_BIDIRECTIONAL))) > > > + { > > > + dma_mark_clean(phys_to_virt(tlb_addr), size); > > > swiotlb_bounce(orig_addr, tlb_addr, size, DMA_FROM_DEVICE); > > > + } > > > > > > /* > > > * Return the buffer to the free list by setting the corresponding > > > @@ -587,17 +591,20 @@ void swiotlb_tbl_sync_single(struct device *hwdev, > > > phys_addr_t tlb_addr, > > > > > > switch (target) { > > > case SYNC_FOR_CPU: > > > - if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)) > > > + if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)) > > > { > > > + dma_mark_clean(phys_to_virt(tlb_addr), size); > > > swiotlb_bounce(orig_addr, tlb_addr, > > > size, DMA_FROM_DEVICE); > > > + } > > > else > > > BUG_ON(dir != DMA_TO_DEVICE); > > > break; > > > case SYNC_FOR_DEVICE: > > > - if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) > > > + if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) { > > > swiotlb_bounce(orig_addr, tlb_addr, > > > size, DMA_TO_DEVICE); > > > - else > > > + dma_mark_clean(phys_to_virt(tlb_addr), size); > > > + } else > > > BUG_ON(dir != DMA_FROM_DEVICE); > > > break; > > > default: > > > -- > > > 1.7.2.5 > > > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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