x86/mm: Fix marking of unused sub-pmd ranges

The unused part precedes the new range spanned by the start, end parameters
of vmemmap_use_new_sub_pmd(). This means it actually goes from
ALIGN_DOWN(start, PMD_SIZE) up to start.

Use the correct address when applying the mark using memset.

Fixes: 74dce834bf69 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
Signed-off-by: Adrian-Ken Rueegsegger <ken@codelabs.ch>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220509090637.24152-2-ken@codelabs.ch

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 96d34ebb20a9e1e09e3a9e8eaf41f464a264d87e..e2942335d1437dc88747052208f34965dc0ef146 100644 (file)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -902,6 +902,8 @@ static void __meminit vmemmap_use_sub_pmd(unsigned long start, unsigned long end
 
 static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end)
 {
+       const unsigned long page = ALIGN_DOWN(start, PMD_SIZE);
+
        vmemmap_flush_unused_pmd();
 
        /*
@@ -914,8 +916,7 @@ static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long
         * Mark with PAGE_UNUSED the unused parts of the new memmap range
         */
        if (!IS_ALIGNED(start, PMD_SIZE))
-               memset((void *)start, PAGE_UNUSED,
-                       start - ALIGN_DOWN(start, PMD_SIZE));
+               memset((void *)page, PAGE_UNUSED, start - page);
 
        /*
         * We want to avoid memset(PAGE_UNUSED) when populating the vmemmap of