xen: map foreign pages for shared rings by updating the PTEs directly

When mapping a foreign page with xenbus_map_ring_valloc() with the
GNTTABOP_map_grant_ref hypercall, set the GNTMAP_contains_pte flag and
pass a pointer to the PTE (in init_mm).

After the page is mapped, the usual fault mechanism can be used to
update additional MMs.  This allows the vmalloc_sync_all() to be
removed from alloc_vm_area().

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
[v1: Squashed fix by Michal for no-mmu case]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 81c3ce6b8bbe..1906125eab49 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -35,6 +35,7 @@
 #include <linux/vmalloc.h>
 #include <linux/export.h>
 #include <asm/xen/hypervisor.h>
+#include <asm/xen/page.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/event_channel.h>
 #include <xen/events.h>
@@ -436,19 +437,20 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
 int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
 {
         struct gnttab_map_grant_ref op = {
-                .flags = GNTMAP_host_map,
+                .flags = GNTMAP_host_map | GNTMAP_contains_pte,
                 .ref   = gnt_ref,
                 .dom   = dev->otherend_id,
         };
         struct vm_struct *area;
+        pte_t *pte;
 
         *vaddr = NULL;
 
-        area = alloc_vm_area(PAGE_SIZE);
+        area = alloc_vm_area(PAGE_SIZE, &pte);
         if (!area)
                 return -ENOMEM;
 
-        op.host_addr = (unsigned long)area->addr;
+        op.host_addr = arbitrary_virt_to_machine(pte).maddr;
 
         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
                 BUG();
@@ -527,6 +529,7 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
         struct gnttab_unmap_grant_ref op = {
                 .host_addr = (unsigned long)vaddr,
         };
+        unsigned int level;
 
         /* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr)
          * method so that we don't have to muck with vmalloc internals here.
@@ -548,6 +551,8 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
         }
 
         op.handle = (grant_handle_t)area->phys_addr;
+        op.host_addr = arbitrary_virt_to_machine(
+                lookup_address((unsigned long)vaddr, &level)).maddr;
 
         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
                 BUG();