linux-kernel - [PATCH RFC 02/11] x86/mm: Factor out phys_pgd

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Message-ID: <20250313-asi-page-alloc-v1-2-04972e046cea@google.com>
Date: Thu, 13 Mar 2025 18:11:21 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Mike Rapoport <rppt@...nel.org>, Junaid Shahid <junaids@...gle.com>, Reiji Watanabe <reijiw@...gle.com>, 
	Patrick Bellasi <derkling@...gle.com>, Brendan Jackman <jackmanb@...gle.com>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH RFC 02/11] 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 01ea7c6df3036bd185cdb3f54ddf244b79cbce8c..8f75274fddd96b8285aff48493ebad93e30daebe 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -731,21 +731,20 @@ 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;
@@ -771,15 +770,29 @@ __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

-- 
2.49.0.rc1.451.g8f38331e32-goog