[Xen-devel] [PATCH 2/3] xen/grant_table: use the new GNTTABOP_unmap_and_replace hypercall

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

The current GNTTABOP_unmap_and_replace (7) is deprecated, rename
it to GNTTABOP_unmap_and_replace_legacy. Introduce the new
GNTTABOP_unmap_and_replace (12) and detect at boot time which one is
available.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CC: alex@xxxxxxxxxxx
CC: dcrisan@xxxxxxxxxxxx
---
 drivers/xen/grant-table.c           |    8 ++++++++
 include/xen/grant_table.h           |    1 +
 include/xen/interface/grant_table.h |    8 +++++---
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 04c1b2d..0f7d00b 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -65,6 +65,8 @@ static grant_ref_t gnttab_free_head;
 static DEFINE_SPINLOCK(gnttab_list_lock);
 unsigned long xen_hvm_resume_frames;
 EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);
+int __read_mostly gnttabop_unmap_and_replace = GNTTABOP_unmap_and_replace; 
+EXPORT_SYMBOL_GPL(gnttabop_unmap_and_replace);
 
 static union {
        struct grant_entry_v1 *v1;
@@ -1238,6 +1240,12 @@ int gnttab_init(void)
        gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
        gnttab_free_head  = NR_RESERVED_ENTRIES;
 
+       ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_and_replace, NULL, 1);
+       if (ret == -ENOSYS) {
+               gnttabop_unmap_and_replace = GNTTABOP_unmap_and_replace_legacy;
+               pr_warn("GNTTABOP_unmap_and_replace unavailable, falling back 
to the racy legacy version\n");
+       }
+
        printk("Grant table initialized\n");
        return 0;
 
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 694dcaf..867d1a7 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -179,6 +179,7 @@ int arch_gnttab_map_status(uint64_t *frames, unsigned long 
nr_gframes,
 void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);
 
 extern unsigned long xen_hvm_resume_frames;
+extern int gnttabop_unmap_and_replace;
 unsigned int gnttab_max_grant_frames(void);
 
 #define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))
diff --git a/include/xen/interface/grant_table.h 
b/include/xen/interface/grant_table.h
index e40fae9..2a2b74f 100644
--- a/include/xen/interface/grant_table.h
+++ b/include/xen/interface/grant_table.h
@@ -408,15 +408,17 @@ DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size);
 /*
  * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings
  * tracked by <handle> but atomically replace the page table entry with one
- * pointing to the machine address under <new_addr>.  <new_addr> will be
- * redirected to the null entry.
+ * pointing to the machine address under <new_addr>.
+ * GNTTABOP_unmap_and_replace_legacy also redirects <new_addr> to the
+ * null entry
  * NOTES:
  *  1. The call may fail in an undefined manner if either mapping is not
  *     tracked by <handle>.
  *  2. After executing a batch of unmaps, it is guaranteed that no stale
  *     mappings will remain in the device or host TLBs.
  */
-#define GNTTABOP_unmap_and_replace    7
+#define GNTTABOP_unmap_and_replace_legacy    7
+#define GNTTABOP_unmap_and_replace    12
 struct gnttab_unmap_and_replace {
     /* IN parameters. */
     uint64_t host_addr;
-- 
1.7.2.5


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