x86, e820, pci: reserve extra free space near end of RAM

The point is to take all RAM resources we have, and
_after_ we've added all the resources we've seen in
the E820 tree, we then _also_ try to add fake reserved
entries for any "round up to X" at the end of the RAM
resources.

[ Impact: improve PCI mem-resource allocation robustness, protect "stolen RAM" ]

Reported-by: Yannick Roehlly <yannick.roehlly@free.fr>
Acked-by: Jesse Barnes <jesse.barnes@intel.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: yannick.roehlly@free.fr
LKML-Reference: <4A01A784.2050407@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 006281302925..a2335d9de052 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1371,6 +1371,23 @@ void __init e820_reserve_resources(void)
         }
 }
 
+/* How much should we pad RAM ending depending on where it is? */
+static unsigned long ram_alignment(resource_size_t pos)
+{
+        unsigned long mb = pos >> 20;
+
+        /* To 64kB in the first megabyte */
+        if (!mb)
+                return 64*1024;
+
+        /* To 1MB in the first 16MB */
+        if (mb < 16)
+                return 1024*1024;
+
+        /* To 32MB for anything above that */
+        return 32*1024*1024;
+}
+
 void __init e820_reserve_resources_late(void)
 {
         int i;
@@ -1382,6 +1399,24 @@ void __init e820_reserve_resources_late(void)
                         insert_resource_expand_to_fit(&iomem_resource, res);
                 res++;
         }
+
+        /*
+         * Try to bump up RAM regions to reasonable boundaries to
+         * avoid stolen RAM:
+         */
+        for (i = 0; i < e820.nr_map; i++) {
+                struct e820entry *entry = &e820_saved.map[i];
+                resource_size_t start, end;
+
+                if (entry->type != E820_RAM)
+                        continue;
+                start = entry->addr + entry->size;
+                end = round_up(start, ram_alignment(start));
+                if (start == end)
+                        continue;
+                reserve_region_with_split(&iomem_resource, start,
+                                                  end - 1, "RAM buffer");
+        }
 }
 
 char *__init default_machine_specific_memory_setup(void)