[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v5 11/13] xen: introduce xen_alloc/free_coherent_pages
On Mon, 9 Sep 2013, Catalin Marinas wrote: > >>> They could also happen in a DomU if we assign a physical device to it > >>> (and an SMMU is not available). > >> > >> The problem is that you don't necessarily know one kind of coherency you > >> know for a physical device. As I said, we plan to do this DT-driven. > > > > OK, but if I call arm64_swiotlb_dma_ops.alloc passing the right > > arguments to it, I should be able to get the right coherency for the > > right device, correct? > > I think it needs a bit more work on the Xen part. Basically > dma_alloc_attrs() calls get_dma_ops() to obtain the best DMA operations > for a device. arm64_swiotlb_dma_ops is just the default implementation > and I'll add a _noncoherent variant as well. Default dma_ops will be > set to one of these during boot. But a device is also allowed to have > its own dev->archdata.dma_ops, set via set_dma_ops(). > > So even if you set the default dma_ops to Xen ops, you may not get them > via dma_alloc_coherent(). I don't see any easier solution other than > patching the dma_alloc_attrs() function to issue a Hyp call after the > memory has been allocated with the get_dma_ops()->alloc(). But I don't > like this either. I see. This problem affects arch/arm as well. Either we add an if (!xen_domain()) in get_dma_ops, or we could make get_dma_ops a function pointer and let people overwrite it. See below the first option implemented for arch/arm on top of the swiotlb series: diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index 7d6e4f9..0b8b5e4 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -12,6 +12,8 @@ #include <asm/memory.h> #include <asm/cacheflush.h> +#include <xen/xen.h> + #define DMA_ERROR_CODE (~0) extern struct dma_map_ops *dma_ops; extern struct dma_map_ops arm_dma_ops; @@ -19,7 +21,7 @@ extern struct dma_map_ops arm_coherent_dma_ops; static inline struct dma_map_ops *get_dma_ops(struct device *dev) { - if (dev && dev->archdata.dma_ops) + if (!xen_domain() && dev && dev->archdata.dma_ops) return dev->archdata.dma_ops; return dma_ops; } diff --git a/arch/arm/include/asm/xen/page-coherent.h b/arch/arm/include/asm/xen/page-coherent.h index af2cf8d..c2232fe 100644 --- a/arch/arm/include/asm/xen/page-coherent.h +++ b/arch/arm/include/asm/xen/page-coherent.h @@ -9,6 +9,8 @@ static inline void *xen_alloc_coherent_pages(struct device *hwdev, size_t size, dma_addr_t *dma_handle, gfp_t flags, struct dma_attrs *attrs) { + if (hwdev && hwdev->archdata.dma_ops) + return hwdev->archdata.dma_ops->alloc(hwdev, size, dma_handle, flags, attrs); return arm_dma_ops.alloc(hwdev, size, dma_handle, flags, attrs); } @@ -16,6 +18,8 @@ static inline void xen_free_coherent_pages(struct device *hwdev, size_t size, void *cpu_addr, dma_addr_t dma_handle, struct dma_attrs *attrs) { + if (hwdev && hwdev->archdata.dma_ops) + return hwdev->archdata.dma_ops->free(hwdev, size, cpu_addr, dma_handle, attrs); return arm_dma_ops.free(hwdev, size, cpu_addr, dma_handle, attrs); } _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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