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

From: Muchun Song <songmuchun@bytedance.com>
To: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
	dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, viro@zeniv.linux.org.uk,
	akpm@linux-foundation.org, paulmck@kernel.org,
	mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com,
	rdunlap@infradead.org, oneukum@suse.com,
	anshuman.khandual@arm.com, jroedel@suse.de,
	almasrymina@google.com, rientjes@google.com, willy@infradead.org,
	osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com
Cc: duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org,
	Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap
Date: Tue, 24 Nov 2020 17:52:50 +0800	[thread overview]
Message-ID: <20201124095259.58755-8-songmuchun@bytedance.com> (raw)
In-Reply-To: <20201124095259.58755-1-songmuchun@bytedance.com>

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@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

