WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 3/3] xen: map foreign pages for shared rings by updat

To: linux-kernel@xxxxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH 3/3] xen: map foreign pages for shared rings by updating the PTEs directly
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Tue, 25 Oct 2011 16:07:59 -0400
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, david.vrabel@xxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Delivery-date: Tue, 25 Oct 2011 13:10:48 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1319573279-13867-1-git-send-email-konrad.wilk@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1319573279-13867-1-git-send-email-konrad.wilk@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
From: David Vrabel <david.vrabel@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/grant-table.c         |    2 +-
 drivers/xen/xenbus/xenbus_client.c |   11 ++++++++---
 include/linux/vmalloc.h            |    2 +-
 mm/vmalloc.c                       |   27 +++++++++++++--------------
 4 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 6bbfd7a..5a40d24 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -71,7 +71,7 @@ int arch_gnttab_map_shared(unsigned long *frames, unsigned 
long nr_gframes,
 
        if (shared == NULL) {
                struct vm_struct *area =
-                       alloc_vm_area(PAGE_SIZE * max_nr_gframes);
+                       alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
                BUG_ON(area == NULL);
                shared = area->addr;
                *__shared = shared;
diff --git a/drivers/xen/xenbus/xenbus_client.c 
b/drivers/xen/xenbus/xenbus_client.c
index 229d3ad..52bc57f 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -34,6 +34,7 @@
 #include <linux/types.h>
 #include <linux/vmalloc.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>
@@ -435,19 +436,20 @@ 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();
@@ -526,6 +528,7 @@ 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.
@@ -547,6 +550,8 @@ 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();
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 9332e52..1a77252 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -118,7 +118,7 @@ unmap_kernel_range(unsigned long addr, unsigned long size)
 #endif
 
 /* Allocate/destroy a 'vmalloc' VM area. */
-extern struct vm_struct *alloc_vm_area(size_t size);
+extern struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes);
 extern void free_vm_area(struct vm_struct *area);
 
 /* for /dev/kmem */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5016f19..b5deec6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2105,23 +2105,30 @@ void  __attribute__((weak)) vmalloc_sync_all(void)
 
 static int f(pte_t *pte, pgtable_t table, unsigned long addr, void *data)
 {
-       /* apply_to_page_range() does all the hard work. */
+       pte_t ***p = data;
+
+       if (p) {
+               *(*p) = pte;
+               (*p)++;
+       }
        return 0;
 }
 
 /**
  *     alloc_vm_area - allocate a range of kernel address space
  *     @size:          size of the area
+ *     @ptes:          returns the PTEs for the address space
  *
  *     Returns:        NULL on failure, vm_struct on success
  *
  *     This function reserves a range of kernel address space, and
  *     allocates pagetables to map that range.  No actual mappings
- *     are created.  If the kernel address space is not shared
- *     between processes, it syncs the pagetable across all
- *     processes.
+ *     are created.
+ *
+ *     If @ptes is non-NULL, pointers to the PTEs (in init_mm)
+ *     allocated for the VM area are returned.
  */
-struct vm_struct *alloc_vm_area(size_t size)
+struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
 {
        struct vm_struct *area;
 
@@ -2135,19 +2142,11 @@ struct vm_struct *alloc_vm_area(size_t size)
         * of kernel virtual address space and mapped into init_mm.
         */
        if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
-                               area->size, f, NULL)) {
+                               size, f, ptes ? &ptes : NULL)) {
                free_vm_area(area);
                return NULL;
        }
 
-       /*
-        * If the allocated address space is passed to a hypercall
-        * before being used then we cannot rely on a page fault to
-        * trigger an update of the page tables.  So sync all the page
-        * tables here.
-        */
-       vmalloc_sync_all();
-
        return area;
 }
 EXPORT_SYMBOL_GPL(alloc_vm_area);
-- 
1.7.6.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel