HVM does not allow direct PTE modification, so instead we request
that Xen change its internal p2m mappings on the allocated pages and
map the memory into userspace normally.
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
drivers/xen/gntdev.c | 117 ++++++++++++++++++++++++++++++++-------------
drivers/xen/grant-table.c | 6 ++
2 files changed, 89 insertions(+), 34 deletions(-)
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 1581403..58fddf3 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -32,6 +32,7 @@
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
+#include <linux/highmem.h>
#include <xen/xen.h>
#include <xen/grant_table.h>
@@ -52,6 +53,8 @@ MODULE_PARM_DESC(limit, "Maximum number of grants that may be
mapped by "
static atomic_t pages_mapped = ATOMIC_INIT(0);
+static int use_ptemod;
+
struct gntdev_priv {
struct list_head maps;
/* lock protects maps from concurrent changes */
@@ -74,6 +77,8 @@ struct grant_map {
struct page **pages;
};
+static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
+
/* ------------------------------------------------------------------ */
static void gntdev_print_maps(struct gntdev_priv *priv,
@@ -179,11 +184,34 @@ static void gntdev_put_map(struct grant_map *map)
atomic_sub(map->count, &pages_mapped);
- if (map->pages)
+ if (map->pages) {
+ if (!use_ptemod)
+ unmap_grant_pages(map, 0, map->count);
+
for (i = 0; i < map->count; i++) {
- if (map->pages[i])
+ uint32_t check, *tmp;
+ if (!map->pages[i])
+ continue;
+ /* XXX When unmapping in an HVM domain, Xen will
+ * sometimes end up mapping the GFN to an invalid MFN.
+ * In this case, writes will be discarded and reads will
+ * return all 0xFF bytes. Leak these unusable GFNs
+ * until Xen supports fixing their p2m mapping.
+ *
+ * Confirmed present in Xen 4.1-RC3 with HVM source
+ */
+ tmp = kmap(map->pages[i]);
+ *tmp = 0xdeaddead;
+ mb();
+ check = *tmp;
+ kunmap(map->pages[i]);
+ if (check == 0xdeaddead)
__free_page(map->pages[i]);
+ else
+ pr_debug("Discard page %d=%ld\n", i,
+ page_to_pfn(map->pages[i]));
}
+ }
kfree(map->pages);
kfree(map->grants);
kfree(map->map_ops);
@@ -197,17 +225,16 @@ static int find_grant_ptes(pte_t *pte, unsigned long
addr, void *data)
{
struct grant_map *map = data;
unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
+ int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;
u64 pte_maddr;
BUG_ON(pgnr >= map->count);
pte_maddr = arbitrary_virt_to_machine(pte).maddr;
- gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr,
- GNTMAP_contains_pte | map->flags,
+ gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
map->grants[pgnr].ref,
map->grants[pgnr].domid);
- gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr,
- GNTMAP_contains_pte | map->flags,
+ gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
0 /* handle */);
return 0;
}
@@ -215,6 +242,19 @@ static int find_grant_ptes(pte_t *pte, unsigned long addr,
void *data)
static int map_grant_pages(struct grant_map *map)
{
int i, err = 0;
+ phys_addr_t addr;
+
+ if (!use_ptemod) {
+ for (i = 0; i < map->count; i++) {
+ addr = (phys_addr_t)
+ pfn_to_kaddr(page_to_pfn(map->pages[i]));
+ gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
+ map->grants[i].ref,
+ map->grants[i].domid);
+ gnttab_set_unmap_op(&map->unmap_ops[i], addr,
+ map->flags, 0 /* handle */);
+ }
+ }
pr_debug("map %d+%d\n", map->index, map->count);
err = gnttab_map_refs(map->map_ops, map->pages, map->count);
@@ -259,17 +299,8 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
gntdev_put_map(map);
}
-static int gntdev_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
-{
- pr_debug("vaddr %p, pgoff %ld (shouldn't happen)\n",
- vmf->virtual_address, vmf->pgoff);
- vmf->flags = VM_FAULT_ERROR;
- return 0;
-}
-
static struct vm_operations_struct gntdev_vmops = {
.close = gntdev_vma_close,
- .fault = gntdev_vma_fault,
};
/* ------------------------------------------------------------------ */
@@ -354,14 +385,16 @@ static int gntdev_open(struct inode *inode, struct file
*flip)
INIT_LIST_HEAD(&priv->maps);
spin_lock_init(&priv->lock);
- priv->mm = get_task_mm(current);
- if (!priv->mm) {
- kfree(priv);
- return -ENOMEM;
+ if (use_ptemod) {
+ priv->mm = get_task_mm(current);
+ if (!priv->mm) {
+ kfree(priv);
+ return -ENOMEM;
+ }
+ priv->mn.ops = &gntdev_mmu_ops;
+ ret = mmu_notifier_register(&priv->mn, priv->mm);
+ mmput(priv->mm);
}
- priv->mn.ops = &gntdev_mmu_ops;
- ret = mmu_notifier_register(&priv->mn, priv->mm);
- mmput(priv->mm);
if (ret) {
kfree(priv);
@@ -389,7 +422,8 @@ static int gntdev_release(struct inode *inode, struct file
*flip)
}
spin_unlock(&priv->lock);
- mmu_notifier_unregister(&priv->mn, priv->mm);
+ if (use_ptemod)
+ mmu_notifier_unregister(&priv->mn, priv->mm);
kfree(priv);
return 0;
}
@@ -514,7 +548,7 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
int index = vma->vm_pgoff;
int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
struct grant_map *map;
- int err = -EINVAL;
+ int i, err = -EINVAL;
if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
return -EINVAL;
@@ -526,9 +560,9 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
map = gntdev_find_map_index(priv, index, count);
if (!map)
goto unlock_out;
- if (map->vma)
+ if (use_ptemod && map->vma)
goto unlock_out;
- if (priv->mm != vma->vm_mm) {
+ if (use_ptemod && priv->mm != vma->vm_mm) {
printk(KERN_WARNING "Huh? Other mm?\n");
goto unlock_out;
}
@@ -540,20 +574,24 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
vma->vm_flags |= VM_RESERVED|VM_DONTCOPY|VM_DONTEXPAND|VM_PFNMAP;
vma->vm_private_data = map;
- map->vma = vma;
- map->flags = GNTMAP_host_map | GNTMAP_application_map;
+ if (use_ptemod)
+ map->vma = vma;
+
+ map->flags = GNTMAP_host_map;
if (!(vma->vm_flags & VM_WRITE))
map->flags |= GNTMAP_readonly;
spin_unlock(&priv->lock);
- err = apply_to_page_range(vma->vm_mm, vma->vm_start,
- vma->vm_end - vma->vm_start,
- find_grant_ptes, map);
- if (err) {
- printk(KERN_WARNING "find_grant_ptes() failure.\n");
- return err;
+ if (use_ptemod) {
+ err = apply_to_page_range(vma->vm_mm, vma->vm_start,
+ vma->vm_end - vma->vm_start,
+ find_grant_ptes, map);
+ if (err) {
+ printk(KERN_WARNING "find_grant_ptes() failure.\n");
+ return err;
+ }
}
err = map_grant_pages(map);
@@ -564,6 +602,15 @@ static int gntdev_mmap(struct file *flip, struct
vm_area_struct *vma)
map->is_mapped = 1;
+ if (!use_ptemod) {
+ for (i = 0; i < count; i++) {
+ err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
+ map->pages[i]);
+ if (err)
+ return err;
+ }
+ }
+
return 0;
unlock_out:
@@ -594,6 +641,8 @@ static int __init gntdev_init(void)
if (!xen_domain())
return -ENODEV;
+ use_ptemod = xen_pv_domain();
+
err = misc_register(&gntdev_miscdev);
if (err != 0) {
printk(KERN_ERR "Could not register gntdev device\n");
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 9ef54eb..9428ced 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -458,6 +458,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
if (ret)
return ret;
+ if (xen_feature(XENFEAT_auto_translated_physmap))
+ return ret;
+
for (i = 0; i < count; i++) {
/* m2p override only supported for GNTMAP_contains_pte mappings
*/
if (!(map_ops[i].flags & GNTMAP_contains_pte))
@@ -483,6 +486,9 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref
*unmap_ops,
if (ret)
return ret;
+ if (xen_feature(XENFEAT_auto_translated_physmap))
+ return ret;
+
for (i = 0; i < count; i++) {
ret = m2p_remove_override(pages[i]);
if (ret)
--
1.7.3.4
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