linux-kernel - [PATCH v2 mm-hotfixes 5/5] x86/mm: drop unnecessary calls to sync_global

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Message-ID: <20250720234203.9126-6-harry.yoo@oracle.com>
Date: Mon, 21 Jul 2025 08:42:03 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...two.org>
Cc: "H . Peter Anvin" <hpa@...or.com>, Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Juergen Gross <jgross@...e.com>, Kevin Brodsky <kevin.brodsky@....com>,
        Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>,
        Joao Martins <joao.m.martins@...cle.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Jane Chu <jane.chu@...cle.com>, Alistair Popple <apopple@...dia.com>,
        Mike Rapoport <rppt@...nel.org>, David Hildenbrand <david@...hat.com>,
        Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, Harry Yoo <harry.yoo@...cle.com>,
        stable@...r.kernel.org
Subject: [PATCH v2 mm-hotfixes 5/5] x86/mm: drop unnecessary calls to sync_global_pgds() and fold into its sole user

Now that p*d_populate_kernel{,init}() handles page table synchronization,
calling sync_global_pgds() is no longer necessary. Remove those
redundant calls.

Additionally, since arch_sync_kernel_mappings() is now the only remaining
caller of sync_global_pgds(), fold the function into its user.

Cc: stable@...r.kernel.org
Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Harry Yoo <harry.yoo@...cle.com>
---
 arch/x86/mm/init_64.c | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index e4922b9c8403..f1507de3b7a3 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -228,7 +228,7 @@ static void sync_global_pgds_l4(unsigned long start, unsigned long end)
  * When memory was added make sure all the processes MM have
  * suitable PGD entries in the local PGD level page.
  */
-static void sync_global_pgds(unsigned long start, unsigned long end)
+void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
 {
 	if (pgtable_l5_enabled())
 		sync_global_pgds_l5(start, end);
@@ -236,11 +236,6 @@ static void sync_global_pgds(unsigned long start, unsigned long end)
 		sync_global_pgds_l4(start, end);
 }
 
-void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
-{
-	sync_global_pgds(start, end);
-}
-
 /*
  * NOTE: This function is marked __ref because it calls __init function
  * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0.
@@ -746,13 +741,11 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
 			       unsigned long page_size_mask,
 			       pgprot_t prot, bool init)
 {
-	bool pgd_changed = false;
-	unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
+	unsigned long vaddr, vaddr_end, vaddr_next, paddr_last;
 
 	paddr_last = paddr_end;
 	vaddr = (unsigned long)__va(paddr_start);
 	vaddr_end = (unsigned long)__va(paddr_end);
-	vaddr_start = vaddr;
 
 	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
 		pgd_t *pgd = pgd_offset_k(vaddr);
@@ -781,12 +774,8 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
 						 (pud_t *) p4d, init);
 
 		spin_unlock(&init_mm.page_table_lock);
-		pgd_changed = true;
 	}
 
-	if (pgd_changed)
-		sync_global_pgds(vaddr_start, vaddr_end - 1);
-
 	return paddr_last;
 }
 
@@ -1580,8 +1569,6 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 		err = -ENOMEM;
 	} else
 		err = vmemmap_populate_basepages(start, end, node, NULL);
-	if (!err)
-		sync_global_pgds(start, end - 1);
 	return err;
 }
 
-- 
2.43.0