[PATCH] xen/memguard: Drop memguard_init() entirely

[Andrew Cooper <andrew.cooper3@citrix.com>]

It is not obvious what this code is doing.  Most of it dates from 2007/2008,
and there have been substantial changes in Xen's memory handling since then.

It was previously optional, and isn't needed for any of the memguard
infrastructure to function.  The use of MAP_SMALL_PAGES causes needless
shattering of superpages.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Tim Deegan <tim@xen.org>
CC: Ian Campbell <Ian.Campbell@citrix.com>
---
 xen/arch/x86/mm.c        | 16 ----------------
 xen/arch/x86/setup.c     |  2 --
 xen/include/asm-arm/mm.h |  1 -
 xen/include/asm-x86/mm.h |  2 --
 4 files changed, 21 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index d6aaed8..ed8ab02 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -6346,22 +6346,6 @@ void free_perdomain_mappings(struct domain *d)
 
 #ifdef MEMORY_GUARD
 
-void memguard_init(void)
-{
-    unsigned long start = max_t(unsigned long, xen_phys_start, 1UL << 20);
-    map_pages_to_xen(
-        (unsigned long)__va(start),
-        start >> PAGE_SHIFT,
-        (__pa(&_end) + PAGE_SIZE - 1 - start) >> PAGE_SHIFT,
-        __PAGE_HYPERVISOR_RW|MAP_SMALL_PAGES);
-    BUG_ON(start != xen_phys_start);
-    map_pages_to_xen(
-        XEN_VIRT_START,
-        start >> PAGE_SHIFT,
-        (__pa(&_end) + PAGE_SIZE - 1 - start) >> PAGE_SHIFT,
-        __PAGE_HYPERVISOR|MAP_SMALL_PAGES);
-}
-
 static void __memguard_change_range(void *p, unsigned long l, int guard)
 {
     unsigned long _p = (unsigned long)p;
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index b8a28d7..cddf954 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1146,8 +1146,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                    ~((1UL << L2_PAGETABLE_SHIFT) - 1);
     destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + BOOTSTRAP_MAP_BASE);
 
-    memguard_init();
-
     nr_pages = 0;
     for ( i = 0; i < e820.nr_map; i++ )
         if ( e820.map[i].type == E820_RAM )
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 2e9d0b2..68cf203 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -331,7 +331,6 @@ unsigned long domain_get_maximum_gpfn(struct domain *d);
 
 extern struct domain *dom_xen, *dom_io, *dom_cow;
 
-#define memguard_init(_s)              (_s)
 #define memguard_guard_stack(_p)       ((void)0)
 #define memguard_guard_range(_p,_l)    ((void)0)
 #define memguard_unguard_range(_p,_l)  ((void)0)
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index a097382..23a4092 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -479,11 +479,9 @@ extern struct rangeset *mmio_ro_ranges;
 #define compat_cr3_to_pfn(cr3) (((unsigned)(cr3) >> 12) | ((unsigned)(cr3) << 20))
 
 #ifdef MEMORY_GUARD
-void memguard_init(void);
 void memguard_guard_range(void *p, unsigned long l);
 void memguard_unguard_range(void *p, unsigned long l);
 #else
-#define memguard_init()                ((void)0)
 #define memguard_guard_range(_p,_l)    ((void)0)
 #define memguard_unguard_range(_p,_l)  ((void)0)
 #endif
-- 
2.1.4