xen/mmu: Release just the MFN list, not MFN list and part of pagetables.

We call memblock_reserve for [start of mfn list] -> [PMD aligned end
of mfn list] instead of <start of mfn list> -> <page aligned end of mfn list].

This has the disastrous effect that if at bootup the end of mfn_list is
not PMD aligned we end up returning to memblock parts of the region
past the mfn_list array. And those parts are the PTE tables with
the disastrous effect of seeing this at bootup:

Write protecting the kernel read-only data: 10240k
Freeing unused kernel memory: 1860k freed
Freeing unused kernel memory: 200k freed
(XEN) mm.c:2429:d0 Bad type (saw 1400000000000002 != exp 7000000000000000) for mfn 116a80 (pfn 14e26)
...
(XEN) mm.c:908:d0 Error getting mfn 116a83 (pfn 14e2a) from L1 entry 8000000116a83067 for l1e_owner=0, pg_owner=0
(XEN) mm.c:908:d0 Error getting mfn 4040 (pfn 5555555555555555) from L1 entry 0000000004040601 for l1e_owner=0, pg_owner=0
.. and so on.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3f8e963b76c0..5b2cb54425ce 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1227,7 +1227,6 @@ static void __init xen_pagetable_setup_done(pgd_t *base)
                         /* We should be in __ka space. */
                         BUG_ON(xen_start_info->mfn_list < __START_KERNEL_map);
                         addr = xen_start_info->mfn_list;
-                        size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
                         /* We roundup to the PMD, which means that if anybody at this stage is
                          * using the __ka address of xen_start_info or xen_start_info->shared_info
                          * they are in going to crash. Fortunatly we have already revectored
@@ -1235,6 +1234,7 @@ static void __init xen_pagetable_setup_done(pgd_t *base)
                         size = roundup(size, PMD_SIZE);
                         xen_cleanhighmap(addr, addr + size);
 
+                        size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
                         memblock_free(__pa(xen_start_info->mfn_list), size);
                         /* And revector! Bye bye old array */
                         xen_start_info->mfn_list = new_mfn_list;