xen: do not release any memory under 1M in domain 0

[net-next-2.6.git] / arch / x86 / xen / setup.c

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index b1dbdaa23ecc2a632003382c0c9e4e1d6819e386..769c4b01fa32e11f01e3a77a37d42f4c8ab13207 100644 (file)
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -118,16 +118,18 @@ static unsigned long __init xen_return_unused_memory(unsigned long max_pfn,
                                                     const struct e820map *e820)
 {
        phys_addr_t max_addr = PFN_PHYS(max_pfn);
-       phys_addr_t last_end = 0;
+       phys_addr_t last_end = ISA_END_ADDRESS;
        unsigned long released = 0;
        int i;
 
+       /* Free any unused memory above the low 1Mbyte. */
        for (i = 0; i < e820->nr_map && last_end < max_addr; i++) {
                phys_addr_t end = e820->map[i].addr;
                end = min(max_addr, end);
 
-               released += xen_release_chunk(last_end, end);
-               last_end = e820->map[i].addr + e820->map[i].size;
+               if (last_end < end)
+                       released += xen_release_chunk(last_end, end);
+               last_end = max(last_end, e820->map[i].addr + e820->map[i].size);
        }
 
        if (last_end < max_addr)
@@ -164,6 +166,7 @@ char * __init xen_memory_setup(void)
                XENMEM_memory_map;
        rc = HYPERVISOR_memory_op(op, &memmap);
        if (rc == -ENOSYS) {
+               BUG_ON(xen_initial_domain());
                memmap.nr_entries = 1;
                map[0].addr = 0ULL;
                map[0].size = mem_end;
@@ -201,12 +204,13 @@ char * __init xen_memory_setup(void)
        }
 
        /*
-        * Even though this is normal, usable memory under Xen, reserve
-        * ISA memory anyway because too many things think they can poke
+        * In domU, the ISA region is normal, usable memory, but we
+        * reserve ISA memory anyway because too many things poke
         * about in there.
         *
-        * In a dom0 kernel, this region is identity mapped with the
-        * hardware ISA area, so it really is out of bounds.
+        * In Dom0, the host E820 information can leave gaps in the
+        * ISA range, which would cause us to release those pages.  To
+        * avoid this, we unconditionally reserve them here.
         */
        e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
                        E820_RESERVED);