A 5-level paging capable machine can have memory above 46-bit in the physical address space. This memory is only addressable in the 5-level paging mode: we don't have enough virtual address space to create direct mapping for such memory in the 4-level paging mode. Currently, we fail boot completely: NULL pointer dereference in subsection_map_init(). Skip creating a memblock for such memory instead and notify user that some memory is not addressable. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # v4.14 --- Tested with a hacked QEMU: https://gist.github.com/kiryl/d45eb54110944ff95e544972d8bdac1d --- arch/x86/kernel/e820.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index c5399e80c59c..022fe1de8940 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -1307,7 +1307,14 @@ void __init e820__memblock_setup(void) if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN) continue; - memblock_add(entry->addr, entry->size); + if (entry->addr >= MAXMEM || end >= MAXMEM) + pr_err_once("Some physical memory is not addressable in the paging mode.\n"); + + if (entry->addr >= MAXMEM) + continue; + + end = min_t(u64, end, MAXMEM - 1); + memblock_add(entry->addr, end - entry->addr); } /* Throw away partial pages: */ -- 2.26.2
