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

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Date:   Tue, 24 Nov 2020 17:52:50 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
        oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
        almasrymina@...gle.com, rientjes@...gle.com, willy@...radead.org,
        osalvador@...e.de, mhocko@...e.com, song.bao.hua@...ilicon.com
Cc:     duanxiongchun@...edance.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap

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 <songmuchun@...edance.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