[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] swiotlb-xen question
Hi, Stefano. Thank You for advice! I see that You just copied the content from the original function arm_dma_mmap() to the swiotlb-xen driver. I've tested the same solution (except that I've copied __get_dma_pgprot() function to the swiotlb-xen.c file too because this function is static in the original file). This solution is working (I've tested it). But there is an easier solution: diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c index b0e77de..f3e820f 100644 --- a/arch/arm/xen/mm.c +++ b/arch/arm/xen/mm.c @@ -48,6 +48,7 @@ static struct dma_map_ops xen_swiotlb_dma_ops = { .sync_sg_for_device = xen_swiotlb_sync_sg_for_device, .map_sg = xen_swiotlb_map_sg_attrs, .unmap_sg = xen_swiotlb_unmap_sg_attrs, + .mmap = arm_dma_mmap, .map_page = xen_swiotlb_map_page, .unmap_page = xen_swiotlb_unmap_page, .dma_supported = xen_swiotlb_dma_supported, The original arm_dma_mmap() function is implemented in the file arch/arm/mm/dma-mapping.c which always is compiled for arm arhitecture. I've checked this solution too. It is working. I have a question. Is my solution correct? Oleksandr Dmytryshyn | Product Engineering and Development GlobalLogic M +38.067.382.2525 www.globallogic.com http://www.globallogic.com/email_disclaimer.txt On Thu, Apr 3, 2014 at 1:51 PM, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote: > On Tue, 1 Apr 2014, Oleksandr Dmytryshyn wrote: >> Hi to all. I've investigated my issue deeper. >> >> Currently we use mmap in 2 cases: video-in (camera) and video-out (display). >> >> In case video-out all is working because mmap callback in the video-out >> device >> leads to the remap_pfn_range() function (this function doesn't use >> unimplemented >> .mmap callback in the swiotlb-xen.c file). >> >> In case video-out mmap callback in the video-in device leads to the .mmap >> callback from the dma ops (unimplemented callback in the swiotlb-xen.c file) >> >> I've investigated kernel code. We have patch from the Stefano Stabellini >> (068a6e62 - arm/xen: get_dma_ops: return xen_dma_ops if we are running as >> xen_initial_domain) >> >> Before this patch the function *get_dma_ops() always returned >> __generic_dma_ops() >> which returned &arm_dma_ops (if archdata.dma_ops is absent). In this case >> for arm architecture .mmap callback is arm_dma_mmap() function. >> >> After this patch for domU all is the same as before this patch. But in case >> dom0 kernel uses xen_dma_ops with unimplemented .mmap callback. If some >> function tries to use .mmap callback in dom0 then kernel calls generic >> function dma_common_mmap() which doesn't work properly. >> >> May be some mechanism for swiotlb-xen should be implemented for unimplemented >> callbacks: if callback is not implemented then right architectural callback >> should be used (.mmap - arm_dma_mmap() for ARM)? > > I understand now. Thanks for investingating! > I think that we'll have to introduce our own version of .mmap, > because dma_to_pfn doesn't work correctly on Xen on ARM. > The implementation would be something like (untested): > > int xen_swiotlb_dma_mmap(struct device *dev, struct vm_area_struct *vma, > void *cpu_addr, dma_addr_t dma_addr, size_t size, > struct dma_attrs *attrs) > { > int ret = -ENXIO; > #ifdef CONFIG_MMU > unsigned long nr_vma_pages = (vma->vm_end - vma->vm_start) >> > PAGE_SHIFT; > unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT; > unsigned long pfn = PFN_DOWN(xen_bus_to_phys(dev, dma_addr)); > unsigned long off = vma->vm_pgoff; > > vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot); > > if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret)) > return ret; > > if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) { > ret = remap_pfn_range(vma, vma->vm_start, > pfn + off, > vma->vm_end - vma->vm_start, > vma->vm_page_prot); > } > #endif /* CONFIG_MMU */ > > return ret; > } > > then we can add the function to xen_swiotlb_dma_ops. > Would you be up for coming up with a proper patch? _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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