[Xen-changelog] [xen-unstable] [LINUX][X86_64] Destroy initial page-table mappings to avoid overlap with modules.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxxxx
# Node ID 40331b1545d2de761b3d4d2777ff9349eceb5c1a
# Parent  a3733a587a9ce1348ef429f4495781592191ec6f
[LINUX][X86_64] Destroy initial page-table mappings to avoid overlap with 
modules.

The temporary mappings needed to set up the 1:1 mappings must be torn
down after use; otherwise they may trigger the
WARN_ON() in vmap_pte_range() (namely if the chunk allocated to hold
kernel and initial page tables gets close to or
exceeds 128Mb, or if a sufficiently high mem= argument causes the
static allocations to grow beyond 128Mb, which in
either case means these mappings extend into the modules area).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
 linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletion(-)

diff -r a3733a587a9c -r 40331b1545d2 
linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c
--- a/linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c    Fri Jun 02 17:54:55 
2006 +0100
+++ b/linux-2.6-xen-sparse/arch/x86_64/mm/init-xen.c    Fri Jun 02 18:06:50 
2006 +0100
@@ -666,7 +666,18 @@ void __meminit init_memory_mapping(unsig
                        set_pgd(pgd_offset_k(start), mk_kernel_pgd(pud_phys));
        }
 
-       BUG_ON(!after_bootmem && start_pfn != table_end);
+       if (!after_bootmem) {
+               BUG_ON(start_pfn != table_end);
+               /*
+                * Destroy the temporary mappings created above. Prevents
+                * overlap with modules area (if init mapping is very big).
+                */
+               start = __START_KERNEL_map + (table_start << PAGE_SHIFT);
+               end   = __START_KERNEL_map + (table_end   << PAGE_SHIFT);
+               for (; start < end; start += PAGE_SIZE)
+                       WARN_ON(HYPERVISOR_update_va_mapping(
+                               start, __pte_ma(0), 0));
+       }
 
        __flush_tlb_all();
 }

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