1 files changed, 33 insertions, 2 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 573e7fe9b147..fa152832e0e6 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -33,6 +33,7 @@
 
 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
 
+#include <linux/bootmem.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
@@ -43,6 +44,7 @@
 #include <linux/hardirq.h>
 #include <linux/workqueue.h>
 #include <linux/ratelimit.h>
+#include <linux/moduleparam.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -52,6 +54,9 @@
 #include <xen/hvc-console.h>
 #include <xen/swiotlb-xen.h>
 #include <xen/balloon.h>
+#ifdef CONFIG_X86
+#include <asm/xen/cpuid.h>
+#endif
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
@@ -68,6 +73,8 @@ static int gnttab_free_count;
 static grant_ref_t gnttab_free_head;
 static DEFINE_SPINLOCK(gnttab_list_lock);
 struct grant_frames xen_auto_xlat_grant_frames;
+static unsigned int xen_gnttab_version;
+module_param_named(version, xen_gnttab_version, uint, 0);
 
 static union {
         struct grant_entry_v1 *v1;
@@ -1177,12 +1184,36 @@ static const struct gnttab_ops gnttab_v2_ops = {
         .query_foreign_access           = gnttab_query_foreign_access_v2,
 };
 
+static bool gnttab_need_v2(void)
+{
+#ifdef CONFIG_X86
+        uint32_t base, width;
+
+        if (xen_pv_domain()) {
+                base = xen_cpuid_base();
+                if (cpuid_eax(base) < 5)
+                        return false;   /* Information not available, use V1. */
+                width = cpuid_ebx(base + 5) &
+                        XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK;
+                return width > 32 + PAGE_SHIFT;
+        }
+#endif
+        return !!(max_possible_pfn >> 32);
+}
+
 static void gnttab_request_version(void)
 {
-        int rc;
+        long rc;
         struct gnttab_set_version gsv;
 
-        gsv.version = 1;
+        if (gnttab_need_v2())
+                gsv.version = 2;
+        else
+                gsv.version = 1;
+
+        /* Boot parameter overrides automatic selection. */
+        if (xen_gnttab_version >= 1 && xen_gnttab_version <= 2)
+                gsv.version = xen_gnttab_version;
 
         rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
         if (rc == 0 && gsv.version == 2)