From 0fee3c95310ec1cd71ff085a3593e9038ae68d08 Mon Sep 17 00:00:00 2001
From: "cl349@freefall.cl.cam.ac.uk" <cl349@freefall.cl.cam.ac.uk>
Date: Tue, 3 Aug 2004 10:56:58 +0000
Subject: [PATCH] bitkeeper revision 1.1108.54.1
 (410f6f7a8sttwKzJ5rdNrGdqP7qDCw)

Make dma_alloc_coherent request contiguous memory from Xen.
---
 .../arch/xen/i386/kernel/pci-dma.c            | 52 +++++++++++++++++--
 1 file changed, 48 insertions(+), 4 deletions(-)

diff --git a/linux-2.6.7-xen-sparse/arch/xen/i386/kernel/pci-dma.c b/linux-2.6.7-xen-sparse/arch/xen/i386/kernel/pci-dma.c
index ab83af48ba..6b604383e8 100644
--- a/linux-2.6.7-xen-sparse/arch/xen/i386/kernel/pci-dma.c
+++ b/linux-2.6.7-xen-sparse/arch/xen/i386/kernel/pci-dma.c
@@ -17,18 +17,62 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
 			   dma_addr_t *dma_handle, int gfp)
 {
 	void *ret;
+	unsigned int order = get_order(size);
+	unsigned long vstart;
+
 	/* ignore region specifiers */
 	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);
 
 	if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;
 
-	ret = (void *)__get_free_pages(gfp, get_order(size));
+	ret = (void *)vstart = __get_free_pages(gfp, order);
+	if (ret == NULL)
+		return ret;
 
-	if (ret != NULL) {
-		memset(ret, 0, size);
-		*dma_handle = virt_to_bus(ret);
+	/*
+	 * Ensure multi-page extents are contiguous in machine memory.
+	 * This code could be cleaned up some, and the number of
+	 * hypercalls reduced.
+	 */
+	if (size > PAGE_SIZE) {
+		pgd_t         *pgd; 
+		pmd_t         *pmd;
+		pte_t         *pte;
+		unsigned long  pfn, i;
+		/* 1. Zap current PTEs, giving away the underlying pages. */
+		for (i = 0; i < (1<<order); i++) {
+			pgd = pgd_offset_k(   (vstart + (i*PAGE_SIZE)));
+			pmd = pmd_offset(pgd, (vstart + (i*PAGE_SIZE)));
+			pte = pte_offset_kernel(pmd, (vstart + (i*PAGE_SIZE)));
+			pfn = pte->pte_low >> PAGE_SHIFT;
+			queue_l1_entry_update(pte, 0);
+			flush_page_update_queue();
+			if (HYPERVISOR_dom_mem_op(MEMOP_decrease_reservation, 
+						  &pfn, 1, 0) != 1) BUG();
+		}
+		/* 2. Get a new contiguous memory extent. */
+		if (HYPERVISOR_dom_mem_op(MEMOP_increase_reservation,
+					  &pfn, 1, order) != 1) BUG();
+		/* 3. Map the new extent in place of old pages. */
+		for (i = 0; i < (1<<order); i++) {
+			pgd = pgd_offset_k(   (vstart + (i*PAGE_SIZE)));
+			pmd = pmd_offset(pgd, (vstart + (i*PAGE_SIZE)));
+			pte = pte_offset_kernel(pmd, (vstart + (i*PAGE_SIZE)));
+			queue_l1_entry_update(
+				pte, ((pfn+i)<<PAGE_SHIFT)|__PAGE_KERNEL);
+			queue_machphys_update(
+				pfn+i, (__pa(ret)>>PAGE_SHIFT)+i);
+			phys_to_machine_mapping[(__pa(ret)>>PAGE_SHIFT)+i] =
+				pfn+i;
+                        flush_page_update_queue();
+		}
+		flush_page_update_queue();
 	}
+
+	memset(ret, 0, size);
+	*dma_handle = virt_to_bus(ret);
+
 	return ret;
 }
 
-- 
2.30.2