linux-kernel - [PATCH 03/21] x86/mm: factor out phys_pgd

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Message-ID: <20250924-b4-asi-page-alloc-v1-3-2d861768041f@google.com>
Date: Wed, 24 Sep 2025 14:59:38 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: jackmanb@...gle.com, Andy Lutomirski <luto@...nel.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
	Johannes Weiner <hannes@...xchg.org>, Zi Yan <ziy@...dia.com>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, Yuanchu Xie <yuanchu@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>
Cc: peterz@...radead.org, bp@...en8.de, dave.hansen@...ux.intel.com, 
	mingo@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org, 
	david@...hat.com, derkling@...gle.com, junaids@...gle.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, reijiw@...gle.com, 
	rientjes@...gle.com, rppt@...nel.org, vbabka@...e.cz, x86@...nel.org, 
	yosry.ahmed@...ux.dev
Subject: [PATCH 03/21] x86/mm: factor out phys_pgd_init()

__kernel_physical_mapping_init() will soon need to work on multiple
PGDs, so factor out something similar to phys_p4d_init() and friends,
which takes the base of the PGD as an argument.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 arch/x86/mm/init_64.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0e4270e20fadb578c7fd6bf5c5e4762027c36c45..e98e85cf15f42db669696ba8195d8fc633351b26 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -741,21 +741,20 @@ phys_p4d_init(p4d_t *p4d_page, unsigned long paddr, unsigned long paddr_end,
 }
 
 static unsigned long __meminit
-__kernel_physical_mapping_init(unsigned long paddr_start,
-			       unsigned long paddr_end,
-			       unsigned long page_size_mask,
-			       pgprot_t prot, bool init)
+phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_end,
+	      unsigned long page_size_mask, pgprot_t prot, bool init, bool *pgd_changed)
 {
-	bool pgd_changed = false;
 	unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
 
+	*pgd_changed = false;
+
 	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);
+		pgd_t *pgd = pgd_offset_pgd(pgd_page, vaddr);
 		p4d_t *p4d;
 
 		vaddr_next = (vaddr & PGDIR_MASK) + PGDIR_SIZE;
@@ -781,15 +780,29 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
 					  (pud_t *) p4d, init);
 
 		spin_unlock(&init_mm.page_table_lock);
-		pgd_changed = true;
+		*pgd_changed = true;
 	}
 
-	if (pgd_changed)
-		sync_global_pgds(vaddr_start, vaddr_end - 1);
-
 	return paddr_last;
 }
 
+static unsigned long __meminit
+__kernel_physical_mapping_init(unsigned long paddr_start,
+			       unsigned long paddr_end,
+			       unsigned long page_size_mask,
+			       pgprot_t prot, bool init)
+{
+	bool pgd_changed;
+	unsigned long paddr_last;
+
+	paddr_last = phys_pgd_init(init_mm.pgd, paddr_start, paddr_end, page_size_mask,
+				   prot, init, &pgd_changed);
+	if (pgd_changed)
+		sync_global_pgds((unsigned long)__va(paddr_start),
+				 (unsigned long)__va(paddr_end) - 1);
+
+	return paddr_last;
+}
 
 /*
  * Create page table mapping for the physical memory for specific physical

-- 
2.50.1