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@linux.intel.com Reviewed-by: Dave Hansen dave.hansen@intel.com Cc: stable@vger.kernel.org # 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?
} /* Throw away partial pages: */ -- 2.26.2
-- Kirill A. Shutemov