[PATCH RFC 02/11] x86/mm: Factor out phys_pgd_init()

From: Brendan Jackman
Date: Thu Mar 13 2025 - 14:12:12 EST


__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@xxxxxxxxxx>
---
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