// SPDX-License-Identifier: GPL-2.0-only /* * Copyright 2010 * by Konrad Rzeszutek Wilk * * This code provides a IOMMU for Xen PV guests with PCI passthrough. * * PV guests under Xen are running in an non-contiguous memory architecture. * * When PCI pass-through is utilized, this necessitates an IOMMU for * translating bus (DMA) to virtual and vice-versa and also providing a * mechanism to have contiguous pages for device drivers operations (say DMA * operations). * * Specifically, under Xen the Linux idea of pages is an illusion. It * assumes that pages start at zero and go up to the available memory. To * help with that, the Linux Xen MMU provides a lookup mechanism to * translate the page frame numbers (PFN) to machine frame numbers (MFN) * and vice-versa. The MFN are the "real" frame numbers. Furthermore * memory is not contiguous. Xen hypervisor stitches memory for guests * from different pools, which means there is no guarantee that PFN==MFN * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are * allocated in descending order (high to low), meaning the guest might * never get any MFN's under the 4GB mark. */ #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #define MAX_DMA_BITS 32 /* * Quick lookup value of the bus address of the IOTLB. */ static inline phys_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr) { unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr)); phys_addr_t baddr = (phys_addr_t)bfn << XEN_PAGE_SHIFT; baddr |= paddr & ~XEN_PAGE_MASK; return baddr; } static inline dma_addr_t xen_phys_to_dma(struct device *dev, phys_addr_t paddr) { return phys_to_dma(dev, xen_phys_to_bus(dev, paddr)); } static inline phys_addr_t xen_bus_to_phys(struct device *dev, phys_addr_t baddr) { unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr)); phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) | (baddr & ~XEN_PAGE_MASK); return paddr; } static inline phys_addr_t xen_dma_to_phys(struct device *dev, dma_addr_t dma_addr) { return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr)); } static inline int range_straddles_page_boundary(phys_addr_t p, size_t size) { unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p); unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size); next_bfn = pfn_to_bfn(xen_pfn); for (i = 1; i < nr_pages; i++) if (pfn_to_bfn(++xen_pfn) != ++next_bfn) return 1; return 0; } static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr) { unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr)); unsigned long xen_pfn = bfn_to_local_pfn(bfn); phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT; /* If the address is outside our domain, it CAN * have the same virtual address as another address * in our domain. Therefore _only_ check address within our domain. */ if (pfn_valid(PFN_DOWN(paddr))) return is_swiotlb_buffer(dev, paddr); return 0; } #ifdef CONFIG_X86 int xen_swiotlb_fixup(void *buf, unsigned long nslabs) { int rc; unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT); unsigned int i, dma_bits = order + PAGE_SHIFT; dma_addr_t dma_handle; phys_addr_t p = virt_to_phys(buf); BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1)); BUG_ON(nslabs % IO_TLB_SEGSIZE); i = 0; do { do { rc = xen_create_contiguous_region( p + (i << IO_TLB_SHIFT), order, dma_bits, &dma_handle); } while (rc && dma_bits++ < MAX_DMA_BITS); if (rc) return rc; i += IO_TLB_SEGSIZE; } while (i < nslabs); return 0; } static void * xen_swiotlb_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs) { u64 dma_mask = dev->coherent_dma_mask; int order = get_order(size); phys_addr_t phys; void *ret; /* Align the allocation to the Xen page size */ size = 1UL << (order + XEN_PAGE_SHIFT); ret = (void *)__get_free_pages(flags, get_order(size)); if (!ret) return ret; phys = virt_to_phys(ret); *dma_handle = xen_phys_to_dma(dev, phys); if (*dma_handle + size - 1 > dma_mask || range_straddles_page_boundary(phys, size)) { if (xen_create_contiguous_region(phys, order, fls64(dma_mask), dma_handle) != 0) goto out_free_pages; SetPageXenRemapped(virt_to_page(ret)); } memset(ret, 0, size); return ret; out_free_pages: free_pages((unsigned long)ret, get_order(size)); return NULL; } static void xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr, dma_addr_t dma_handle, unsigned long attrs) { phys_addr_t phys = virt_to_phys(vaddr); int order = get_order(size); /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT); if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) || WARN_ON_ONCE(range_straddles_page_boundary(phys, size))) return; if (TestClearPageXenRemapped(virt_to_page(vaddr))) xen_destroy_contiguous_region(phys, order); free_pages((unsigned long)vaddr, get_order(size)); } #endif /* CONFIG_X86 */ /* * Map a single buffer of the indicated size for DMA in streaming mode. The * physical address to use is returned. * * Once the device is given the dma address, the device owns this memory until * either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed. */ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, unsigned long offset, size_t size, enum dma_data_direction dir, unsigned long attrs) { phys_addr_t map, phys = page_to_phys(page) + offset; dma_addr_t dev_addr = xen_phys_to_dma(dev, phys); BUG_ON(dir == DMA_NONE); /* * If the address happens to be in the device's DMA window, * we can safely return the device addr and not worry about bounce * buffering it. */ if (dma_capable(dev, dev_addr, size, true) && !range_straddles_page_boundary(phys, size) && !xen_arch_need_swiotlb(dev, phys, dev_addr) && !is_swiotlb_force_bounce(dev)) goto done; /* * Oh well, have to allocate and map a bounce buffer. */ trace_swiotlb_bounced(dev, dev_addr, size); map = swiotlb_tbl_map_single(dev, phys, size, size, 0, dir, attrs); if (map == (phys_addr_t)DMA_MAPPING_ERROR) return DMA_MAPPING_ERROR; phys = map; dev_addr = xen_phys_to_dma(dev, map); /* * Ensure that the address returned is DMA'ble */ if (unlikely(!dma_capable(dev, dev_addr, size, true))) { swiotlb_tbl_unmap_single(dev, map, size, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC); return DMA_MAPPING_ERROR; } done: if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr)))) arch_sync_dma_for_device(phys, size, dir); else xen_dma_sync_for_device(dev, dev_addr, size, dir); } return dev_addr; } /* * Unmap a single streaming mode DMA translation. The dma_addr and size must * match what was provided for in a previous xen_swiotlb_map_page call. All * other usages are undefined. * * After this call, reads by the cpu to the buffer are guaranteed to see * whatever the device wrote there. */ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr, size_t size, enum dma_data_direction dir, unsigned long attrs) { phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr); BUG_ON(dir == DMA_NONE); if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr)))) arch_sync_dma_for_cpu(paddr, size, dir); else xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir); } /* NOTE: We use dev_addr here, not paddr! */ if (is_xen_swiotlb_buffer(hwdev, dev_addr)) swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs); } static void xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr, size_t size, enum dma_data_direction dir) { phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr); if (!dev_is_dma_coherent(dev)) { if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr)))) arch_sync_dma_for_cpu(paddr, size, dir); else xen_dma_sync_for_cpu(dev, dma_addr, size, dir); } if (is_xen_swiotlb_buffer(dev, dma_addr)) swiotlb_sync_single_for_cpu(dev, paddr, size, dir); } static void xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr, size_t size, enum dma_data_direction dir) { phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr); if (is_xen_swiotlb_buffer(dev, dma_addr)) swiotlb_sync_single_for_device(dev, paddr, size, dir); if (!dev_is_dma_coherent(dev)) { if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr)))) arch_sync_dma_for_device(paddr, size, dir); else xen_dma_sync_for_device(dev, dma_addr, size, dir); } } /* * Unmap a set of streaming mode DMA translations. Again, cpu read rules * concerning calls here are the same as for swiotlb_unmap_page() above. */ static void xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems, enum dma_data_direction dir, unsigned long attrs) { struct scatterlist *sg; int i; BUG_ON(dir == DMA_NONE); for_each_sg(sgl, sg, nelems, i) xen_swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg), dir, attrs); } static int xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems, enum dma_data_direction dir, unsigned long attrs) { struct scatterlist *sg; int i; BUG_ON(dir == DMA_NONE); for_each_sg(sgl, sg, nelems, i) { sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg), sg->offset, sg->length, dir, attrs); if (sg->dma_address == DMA_MAPPING_ERROR) goto out_unmap; sg_dma_len(sg) = sg->length; } return nelems; out_unmap: xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC); sg_dma_len(sgl) = 0; return -EIO; } static void xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl, int nelems, enum dma_data_direction dir) { struct scatterlist *sg; int i; for_each_sg(sgl, sg, nelems, i) { xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address, sg->length, dir); } } static void xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl, int nelems, enum dma_data_direction dir) { struct scatterlist *sg; int i; for_each_sg(sgl, sg, nelems, i) { xen_swiotlb_sync_single_for_device(dev, sg->dma_address, sg->length, dir); } } /* * Return whether the given device DMA address mask can be supported * properly. For example, if your device can only drive the low 24-bits * during bus mastering, then you would pass 0x00ffffff as the mask to * this function. */ static int xen_swiotlb_dma_supported(struct device *hwdev, u64 mask) { return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask; } const struct dma_map_ops xen_swiotlb_dma_ops = { #ifdef CONFIG_X86 .alloc = xen_swiotlb_alloc_coherent, .free = xen_swiotlb_free_coherent, #else .alloc = dma_direct_alloc, .free = dma_direct_free, #endif .sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu, .sync_single_for_device = xen_swiotlb_sync_single_for_device, .sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu, .sync_sg_for_device = xen_swiotlb_sync_sg_for_device, .map_sg = xen_swiotlb_map_sg, .unmap_sg = xen_swiotlb_unmap_sg, .map_page = xen_swiotlb_map_page, .unmap_page = xen_swiotlb_unmap_page, .dma_supported = xen_swiotlb_dma_supported, .mmap = dma_common_mmap, .get_sgtable = dma_common_get_sgtable, .alloc_pages = dma_common_alloc_pages, .free_pages = dma_common_free_pages, };