On Mon, May 25, 2020 at 05:59:43PM +0300, Mike Rapoport wrote: > On Mon, May 25, 2020 at 07:49:02AM +0300, Kirill A. Shutemov wrote: > > On Mon, May 11, 2020 at 10:17:21PM +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 > > > --- > > > > Gentle ping. > > > > It's not urgent, but it's a bug fix. Please consider applying. > > > > > Tested with a hacked QEMU: https://gist.github.com/kiryl/d45eb54110944ff95e544972d8bdac1d > > > > > > --- > > > arch/x86/kernel/e820.c | 19 +++++++++++++++++-- > > > 1 file changed, 17 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > > > index c5399e80c59c..d320d37d0f95 100644 > > > --- a/arch/x86/kernel/e820.c > > > +++ b/arch/x86/kernel/e820.c > > > @@ -1280,8 +1280,8 @@ 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 +1307,22 @@ 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) { > > > + pr_err("%lldGB of physical memory is not addressable in the paging mode\n", > > > + not_addressable >> 30); > > > + if (!pgtable_l5_enabled()) > > > + pr_err("Consider enabling 5-level paging\n"); > > Could this happen at all when l5 is enabled? > Does it mean we need kmap() for 64-bit? It's future-profing. Who knows what paging modes we would have in the future. -- Kirill A. Shutemov
