x86: fix init_memory_mapping() to handle small ranges

Impact: fix failed EFI bootup in certain circumstances

Ying Huang found init_memory_mapping() has problem with small ranges
less than 2M when he tried to direct map the EFI runtime code out of
max_low_pfn_mapped.

It turns out we never considered that case and didn't check the range...

Reported-by: Ying Huang <ying.huang@intel.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Brian Maly <bmaly@redhat.com>
LKML-Reference: <49ACDDED.1060508@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index e6d36b490250..b1352250096e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -714,6 +714,8 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
         pos = start_pfn << PAGE_SHIFT;
         end_pfn = ((pos + (PMD_SIZE - 1)) >> PMD_SHIFT)
                         << (PMD_SHIFT - PAGE_SHIFT);
+        if (end_pfn > (end >> PAGE_SHIFT))
+                end_pfn = end >> PAGE_SHIFT;
         if (start_pfn < end_pfn) {
                 nr_range = save_mr(mr, nr_range, start_pfn, end_pfn, 0);
                 pos = end_pfn << PAGE_SHIFT;