gntdev: steal in-domain memory for HVM mappings

index a33e443..d783da8 100644
@@ -25,6 +25,7 @@
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/mmu_notifier.h>
+#include <linux/vmalloc.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
 #include <linux/sched.h>

@@ -67,6 +68,7 @@ struct grant_map {
 	struct ioctl_gntdev_grant_ref *grants;
 	struct gnttab_map_grant_ref   *map_ops;
 	struct gnttab_unmap_grant_ref *unmap_ops;
+	void* start;
 };
 
 /* ------------------------------------------------------------------ */

@@ -95,6 +97,7 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
 	add->grants    = kzalloc(sizeof(add->grants[0])    * count, GFP_KERNEL);
 	add->map_ops   = kzalloc(sizeof(add->map_ops[0])   * count, GFP_KERNEL);
 	add->unmap_ops = kzalloc(sizeof(add->unmap_ops[0]) * count, GFP_KERNEL);
+	add->start = NULL;
 	if (NULL == add->grants  ||
 	    NULL == add->map_ops ||
 	    NULL == add->unmap_ops)

@@ -187,6 +190,7 @@ static void gntdev_free_map(struct grant_map *map)
 {
 	if (!map)
 		return;
+	vfree(map->start);
 	kfree(map->grants);
 	kfree(map->map_ops);
 	kfree(map->unmap_ops);

@@ -212,6 +216,24 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token, unsigned long addr, void
 	return 0;
 }
 
+static int hvm_setup_grant_ops(struct grant_map *map)
+{
+	int i;
+	map->start = vmalloc(map->count << PAGE_SHIFT);
+	if (!map->start)
+		return -ENOMEM;
+
+	for(i = 0; i < map->count; i++) {
+		void* address = map->start + (i << PAGE_SHIFT);
+		u64 mfn = (u64)pfn_to_kaddr(vmalloc_to_pfn(address));
+		gnttab_set_map_op(&map->map_ops[i], mfn, map->flags,
+		                  map->grants[i].ref, map->grants[i].domid);
+		gnttab_set_unmap_op(&map->unmap_ops[i], mfn, map->flags, 0);
+	}
+
+	return 0;
+}
+
 static int map_grant_pages(struct grant_map *map)
 {
 	int i, err = 0;

@@ -266,10 +288,27 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
 
 static int gntdev_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-	if (debug)
-		printk("%s: vaddr %p, pgoff %ld (shouldn't happen)\n",
-		       __FUNCTION__, vmf->virtual_address, vmf->pgoff);
-	vmf->flags = VM_FAULT_ERROR;
+	struct page *page;
+	struct grant_map *map = vma->vm_private_data;
+	pgoff_t pgoff = vmf->pgoff - vma->vm_pgoff;
+	
+	if (!map || !map->start) {
+		if (debug)
+			printk("%s: vaddr %p, pgoff %ld (shouldn't happen)\n",
+				__FUNCTION__, vmf->virtual_address, pgoff);
+		return VM_FAULT_SIGBUS;
+	}
+
+	if (pgoff < 0 || pgoff > map->count)
+		return VM_FAULT_SIGBUS;
+
+	page = vmalloc_to_page(map->start + (pgoff << PAGE_SHIFT));
+	if (!page)
+		return VM_FAULT_SIGBUS;
+	
+	get_page(page);
+	vmf->page = page;
+
 	return 0;
 }
 

@@ -573,29 +612,33 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 	vma->vm_flags |= VM_RESERVED;
 	vma->vm_flags |= VM_DONTCOPY;
 	vma->vm_flags |= VM_DONTEXPAND;
+	vma->vm_flags |= VM_FOREIGN;
 
 	vma->vm_private_data = map;
 	map->vma = vma;
 
-	map->flags = GNTMAP_host_map | GNTMAP_application_map | GNTMAP_contains_pte;
+	map->flags = GNTMAP_host_map;
 	if (!(vma->vm_flags & VM_WRITE))
 		map->flags |= GNTMAP_readonly;
 
-	err = apply_to_page_range(vma->vm_mm, vma->vm_start,
-				  vma->vm_end - vma->vm_start,
-				  find_grant_ptes, map);
-	if (err) {
-		goto unlock_out;
-		if (debug)
-			printk("%s: find_grant_ptes() failure.\n", __FUNCTION__);
+	if (xen_pv_domain()) {
+		// Add foreign mapping by page table modification
+		map->flags |= GNTMAP_application_map | GNTMAP_contains_pte;
+
+		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
+					  vma->vm_end - vma->vm_start,
+					  find_grant_ptes, map);
+	} else {
+		// Add mapping by sharing in-domain memory
+		err = hvm_setup_grant_ops(map);
 	}
+	if (err)
+		goto unlock_out;
 
 	err = map_grant_pages(map);
-	if (err) {
+	if (err)
 		goto unlock_out;
-		if (debug)
-			printk("%s: map_grant_pages() failure.\n", __FUNCTION__);
-	}
+
 	map->is_mapped = 1;
 
 unlock_out: