[Xen-devel] [PATCH 07/14] xen: mark grant mapped pages as foreign

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: Jenny Herbert <jennifer.herbert@xxxxxxxxxx>

Use the "foreign" page flag to mark pages that have a grant map.  Use
page->private to store information of the grant (the granting domain
and the grant reference).

Signed-off-by: Jenny Herbert <jenny.herbert@xxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 arch/x86/xen/p2m.c        |    7 -------
 drivers/xen/grant-table.c |   43 +++++++++++++++++++++++++++++++++++++++++--
 include/xen/grant_table.h |   20 ++++++++++++++++++++
 3 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 0d70814..b717168 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -681,12 +681,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref 
*map_ops,
                }
                pfn = page_to_pfn(pages[i]);
 
-               WARN_ON(PagePrivate(pages[i]));
                WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be 
ballooned");
 
-               SetPagePrivate(pages[i]);
-               set_page_private(pages[i], mfn);
-
                if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
                        ret = -ENOMEM;
                        goto out;
@@ -716,9 +712,6 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref 
*unmap_ops,
                        goto out;
                }
 
-               set_page_private(pages[i], INVALID_P2M_ENTRY);
-               WARN_ON(!PagePrivate(pages[i]));
-               ClearPagePrivate(pages[i]);
                set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
        }
        if (kunmap_ops)
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 8d6e97c..9c7dc75 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -679,12 +679,27 @@ EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
  */
 int gnttab_alloc_pages(int nr_pages, struct page **pages)
 {
+       int i;
        int ret;
 
        ret = alloc_xenballooned_pages(nr_pages, pages, false);
        if (ret < 0)
                return ret;
 
+       for (i = 0; i < nr_pages; i++) {
+#if BITS_PER_LONG < 64
+               struct xen_page_foreign *foreign;
+
+               foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
+               if (!foreign) {
+                       gnttab_free_pages(nr_pages, pages);
+                       return -ENOMEM;
+               }
+               set_page_set_private(pages[i], (unsigned long)foreign);
+#endif
+               SetPagePrivate(pages[i]);
+       }
+
        return 0;
 }
 
@@ -695,6 +710,16 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
  */
 void gnttab_free_pages(int nr_pages, struct page **pages)
 {
+       int i;
+
+       for (i = 0; i < nr_pages; i++) {
+               if (PagePrivate(pages[i])) {
+#if BITS_PER_LONG < 64
+                       kfree((void *)page_private(pages[i]));
+#endif
+                       ClearPagePrivate(pages[i]);
+               }
+       }
        free_xenballooned_pages(nr_pages, pages);
 }
 
@@ -754,12 +779,22 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
        if (ret)
                return ret;
 
-       /* Retry eagain maps */
-       for (i = 0; i < count; i++)
+       for (i = 0; i < count; i++) {
+               /* Retry eagain maps */
                if (map_ops[i].status == GNTST_eagain)
                        gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops 
+ i,
                                                &map_ops[i].status, __func__);
 
+               if (map_ops[i].status == GNTST_okay) {
+                       struct xen_page_foreign *foreign;
+
+                       SetPageForeign(pages[i]);
+                       foreign = xen_page_foreign(pages[i]);
+                       foreign->domid = map_ops[i].dom;
+                       foreign->gref = map_ops[i].ref;
+               }
+       }
+
        return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
@@ -768,12 +803,16 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref 
*unmap_ops,
                      struct gnttab_unmap_grant_ref *kunmap_ops,
                      struct page **pages, unsigned int count)
 {
+       unsigned int i;
        int ret;
 
        ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, 
count);
        if (ret)
                return ret;
 
+       for (i = 0; i < count; i++)
+               ClearPageForeign(pages[i]);
+
        return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 949803e..d3bef56 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -45,6 +45,8 @@
 #include <asm/xen/hypervisor.h>
 
 #include <xen/features.h>
+#include <linux/mm_types.h>
+#include <linux/page-flags.h>
 
 #define GNTTAB_RESERVED_XENSTORE 1
 
@@ -185,4 +187,22 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref 
*unmap_ops,
 void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count);
 void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count);
 
+
+struct xen_page_foreign {
+       domid_t domid;
+       grant_ref_t gref;
+};
+
+static inline struct xen_page_foreign *xen_page_foreign(struct page *page)
+{
+       if (!PageForeign(page))
+               return NULL;
+#if BITS_PER_LONG < 64
+       return (struct xen_page_foreign *)page->private;
+#else
+       BUILD_BUG_ON(sizeof(struct xen_page_foreign) > BITS_PER_LONG);
+       return (struct xen_page_foreign *)&page->private;
+#endif
+}
+
 #endif /* __ASM_GNTTAB_H__ */
-- 
1.7.10.4


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