1 files changed, 143 insertions, 0 deletions
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
new file mode 100644
index 000000000..3d826c0b5
--- /dev/null
+++ b/arch/arm/xen/mm.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/cpu.h>
+#include <linux/dma-direct.h>
+#include <linux/dma-map-ops.h>
+#include <linux/gfp.h>
+#include <linux/highmem.h>
+#include <linux/export.h>
+#include <linux/memblock.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <linux/swiotlb.h>
+
+#include <xen/xen.h>
+#include <xen/interface/grant_table.h>
+#include <xen/interface/memory.h>
+#include <xen/page.h>
+#include <xen/xen-ops.h>
+#include <xen/swiotlb-xen.h>
+
+#include <asm/cacheflush.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/interface.h>
+
+static gfp_t xen_swiotlb_gfp(void)
+{
+	phys_addr_t base;
+	u64 i;
+
+	for_each_mem_range(i, &base, NULL) {
+		if (base < (phys_addr_t)0xffffffff) {
+			if (IS_ENABLED(CONFIG_ZONE_DMA32))
+				return __GFP_DMA32;
+			return __GFP_DMA;
+		}
+	}
+
+	return GFP_KERNEL;
+}
+
+static bool hypercall_cflush = false;
+
+/* buffers in highmem or foreign pages cannot cross page boundaries */
+static void dma_cache_maint(struct device *dev, dma_addr_t handle,
+			    size_t size, u32 op)
+{
+	struct gnttab_cache_flush cflush;
+
+	cflush.offset = xen_offset_in_page(handle);
+	cflush.op = op;
+	handle &= XEN_PAGE_MASK;
+
+	do {
+		cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
+
+		if (size + cflush.offset > XEN_PAGE_SIZE)
+			cflush.length = XEN_PAGE_SIZE - cflush.offset;
+		else
+			cflush.length = size;
+
+		HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
+
+		cflush.offset = 0;
+		handle += cflush.length;
+		size -= cflush.length;
+	} while (size);
+}
+
+/*
+ * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
+ * pages, it is not possible for it to contain a mix of local and foreign Xen
+ * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
+ * pfn_valid returns true the pages is local and we can use the native
+ * dma-direct functions, otherwise we call the Xen specific version.
+ */
+void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
+			  size_t size, enum dma_data_direction dir)
+{
+	if (dir != DMA_TO_DEVICE)
+		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
+}
+
+void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
+			     size_t size, enum dma_data_direction dir)
+{
+	if (dir == DMA_FROM_DEVICE)
+		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
+	else
+		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
+}
+
+bool xen_arch_need_swiotlb(struct device *dev,
+			   phys_addr_t phys,
+			   dma_addr_t dev_addr)
+{
+	unsigned int xen_pfn = XEN_PFN_DOWN(phys);
+	unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr));
+
+	/*
+	 * The swiotlb buffer should be used if
+	 *	- Xen doesn't have the cache flush hypercall
+	 *	- The Linux page refers to foreign memory
+	 *	- The device doesn't support coherent DMA request
+	 *
+	 * The Linux page may be spanned acrros multiple Xen page, although
+	 * it's not possible to have a mix of local and foreign Xen page.
+	 * Furthermore, range_straddles_page_boundary is already checking
+	 * if buffer is physically contiguous in the host RAM.
+	 *
+	 * Therefore we only need to check the first Xen page to know if we
+	 * require a bounce buffer because the device doesn't support coherent
+	 * memory and we are not able to flush the cache.
+	 */
+	return (!hypercall_cflush && (xen_pfn != bfn) &&
+		!dev_is_dma_coherent(dev));
+}
+
+static int __init xen_mm_init(void)
+{
+	struct gnttab_cache_flush cflush;
+	int rc;
+
+	if (!xen_swiotlb_detect())
+		return 0;
+
+	/* we can work with the default swiotlb */
+	if (!io_tlb_default_mem.nslabs) {
+		rc = swiotlb_init_late(swiotlb_size_or_default(),
+				       xen_swiotlb_gfp(), NULL);
+		if (rc < 0)
+			return rc;
+	}
+
+	cflush.op = 0;
+	cflush.a.dev_bus_addr = 0;
+	cflush.offset = 0;
+	cflush.length = 0;
+	if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
+		hypercall_cflush = true;
+	return 0;
+}
+arch_initcall(xen_mm_init);