On Tue, 19 Apr 2022 20:29:27 +0200 Ard Biesheuvel [off-list ref] wrote:

quoted

quoted

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)

                      usable_startpfn = memblock_region_memory_base_pfn(r);

-                     if (usable_startpfn < 0x100000) {
+                     if (usable_startpfn < PHYS_PFN(SZ_4G)) {
                              mem_below_4gb_not_mirrored = true;
                              continue;
                      }

Regardless PFN value should never be encoded directly.

Reviewed-by: Anshuman Khandual <redacted>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Andrew, can you please take this one through the -mm tree? The rest of
the series needs a bit more work, but is an obvious fix and there is
no point in holding it up.

Sure.

I'm not seeing any description of the runtime effects of this
shortcoming.  I tentatively queued the fix for 5.18, without a
cc:stable for backporting.  But that might not be the best decision?