Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404Ab3JBRcn (ORCPT ); Wed, 2 Oct 2013 13:32:43 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:5693 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754894Ab3JBRcm (ORCPT ); Wed, 2 Oct 2013 13:32:42 -0400 X-IronPort-AV: E=Sophos;i="4.90,1019,1371081600"; d="scan'208";a="57052508" Date: Wed, 2 Oct 2013 18:31:57 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Konrad Rzeszutek Wilk CC: Stefano Stabellini , , , , Subject: Re: [PATCH v6 12/19] swiotlb: don't assume that io_tlb_start-io_tlb_end is coherent In-Reply-To: <20130930155617.GS3106@phenom.dumpdata.com> Message-ID: References: <1380298207-29151-12-git-send-email-stefano.stabellini@eu.citrix.com> <20130930155617.GS3106@phenom.dumpdata.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3813 Lines: 96 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 > > Signed-off-by: Stefano Stabellini > > --- > > 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 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/