[PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap

[Muchun Song]

If we enable the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, we can just
disbale PMD page mapping of vmemmap to simplify the code. In this
case, we do not need complex code doing vmemmap page table
manipulation. This is a way to simply the first version of this
patch series. In the future, we can add some code doing page table
manipulation.

Signed-off-by: Muchun Song <songmuc...@bytedance.com>
---
 arch/x86/mm/init_64.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0435bee2e172..155cb06a6961 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1557,7 +1557,9 @@ int __meminit vmemmap_populate(unsigned long start, 
unsigned long end, int node,
 {
        int err;
 
-       if (end - start < PAGES_PER_SECTION * sizeof(struct page))
+       if (IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP))
+               err = vmemmap_populate_basepages(start, end, node, NULL);
+       else if (end - start < PAGES_PER_SECTION * sizeof(struct page))
                err = vmemmap_populate_basepages(start, end, node, NULL);
        else if (boot_cpu_has(X86_FEATURE_PSE))
                err = vmemmap_populate_hugepages(start, end, node, altmap);
@@ -1610,7 +1612,8 @@ void register_page_bootmem_memmap(unsigned long 
section_nr,
                }
                get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
 
-               if (!boot_cpu_has(X86_FEATURE_PSE)) {
+               if (!boot_cpu_has(X86_FEATURE_PSE) ||
+                   IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)) {
                        next = (addr + PAGE_SIZE) & PAGE_MASK;
                        pmd = pmd_offset(pud, addr);
                        if (pmd_none(*pmd))
-- 
2.11.0