On Mon, Jun 08, 2020 at 03:54:23PM +0300, Kirill A. Shutemov wrote:
> 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>
> Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v4.14
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> ---
> arch/x86/kernel/e820.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index c5399e80c59c..c10bab121916 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -16,6 +16,7 @@
> #include <linux/firmware-map.h>
> #include <linux/sort.h>
> #include <linux/memory_hotplug.h>
> +#include <linux/string_helpers.h>
>
> #include <asm/e820/api.h>
> #include <asm/setup.h>
> @@ -1280,8 +1281,8 @@ void __init e820__memory_setup(void)
>
> void __init e820__memblock_setup(void)
> {
> + u64 size, end, not_addressable = 0;
> int i;
> - u64 end;
>
> /*
> * The bootstrap memblock region count maximum is 128 entries
> @@ -1307,7 +1308,26 @@ 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) {
> + not_addressable += entry->size;
> + continue;
> + }
> +
> + end = min_t(u64, end, MAXMEM - 1);
> + size = end - entry->addr;
> + not_addressable += entry->size - size;
> + memblock_add(entry->addr, size);
> + }
> +
> + if (not_addressable) {
> + char tmp[10];
> +
> + string_get_size(not_addressable, 1, STRING_UNITS_2, tmp, sizeof(tmp));
> + pr_err("%s of physical memory is not addressable in the %s paging mode\n",
> + tmp, pgtable_l5_enabled() ? "5-level" : "4-level");
> +
> + if (!pgtable_l5_enabled())
> + pr_err("Consider enabling 5-level paging\n");
> }
>
> /* Throw away partial pages: */
> --
> 2.26.2
>
>
--
Sincerely yours,
Mike.
