[PATCH v3 50/60] arm64: mm: Add 5 level paging support to fixmap and swapper handling

Ard Biesheuvel
2023-03-07T14:12:08Z

Add support for using 5 levels of paging in the fixmap, as well as in
the kernel page table handling code which uses fixmaps internally.
This also handles the case where a 5 level build runs on hardware that
only supports 4 levels of paging.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/fixmap.h | 1 +
arch/arm64/include/asm/pgtable.h | 45 ++++++++++++--
arch/arm64/mm/mmu.c | 64 +++++++++++++++++---
3 files changed, 96 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 71ed5fdf718bd0fd..8d4ec7bf74afb7a6 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -90,6 +90,7 @@ enum fixed_addresses {
FIX_PTE,
FIX_PMD,
FIX_PUD,
+ FIX_P4D,
FIX_PGD,

__end_of_fixed_addresses
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index c667073e3f56755d..a286ecc447d33b24 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -613,12 +613,12 @@ static inline bool pud_table(pud_t pud) { return true; }
PUD_TYPE_TABLE)
#endif

-extern pgd_t init_pg_dir[PTRS_PER_PGD];
+extern pgd_t init_pg_dir[];
extern pgd_t init_pg_end[];
-extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
-extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
-extern pgd_t tramp_pg_dir[PTRS_PER_PGD];
-extern pgd_t reserved_pg_dir[PTRS_PER_PGD];
+extern pgd_t swapper_pg_dir[];
+extern pgd_t idmap_pg_dir[];
+extern pgd_t tramp_pg_dir[];
+extern pgd_t reserved_pg_dir[];

extern void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd);

@@ -883,12 +883,47 @@ static inline p4d_t *p4d_offset(pgd_t *pgdp, unsigned long addr)
return p4d_offset_lockless(pgdp, READ_ONCE(*pgdp), addr);
}

+static inline p4d_t *p4d_set_fixmap(unsigned long addr)
+{
+ if (!pgtable_l5_enabled())
+ return NULL;
+ return (p4d_t *)set_fixmap_offset(FIX_P4D, addr);
+}
+
+static inline p4d_t *p4d_set_fixmap_offset(pgd_t *pgdp, unsigned long addr)
+{
+ if (!pgtable_l5_enabled())
+ return pgd_to_folded_p4d(pgdp, addr);
+ return p4d_set_fixmap(p4d_offset_phys(pgdp, addr));
+}
+
+static inline void p4d_clear_fixmap(void)
+{
+ if (pgtable_l5_enabled())
+ clear_fixmap(FIX_P4D);
+}
+
+/* use ONLY for statically allocated translation tables */
+static inline p4d_t *p4d_offset_kimg(pgd_t *pgdp, u64 addr)
+{
+ if (!pgtable_l5_enabled())
+ return pgd_to_folded_p4d(pgdp, addr);
+ return (p4d_t *)__phys_to_kimg(p4d_offset_phys(pgdp, addr));
+}
+
#define pgd_page(pgd) pfn_to_page(__phys_to_pfn(__pgd_to_phys(pgd)))

#else

static inline bool pgtable_l5_enabled(void) { return false; }

+/* Match p4d_offset folding in <asm/generic/pgtable-nop4d.h> */
+#define p4d_set_fixmap(addr) NULL
+#define p4d_set_fixmap_offset(p4dp, addr) ((p4d_t *)p4dp)
+#define p4d_clear_fixmap()
+
+#define p4d_offset_kimg(dir,addr) ((p4d_t *)dir)
+
#endif /* CONFIG_PGTABLE_LEVELS > 4 */

#define pgd_ERROR(e) \
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 6426df5211456cfe..77cd163375124c6a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -315,15 +315,14 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
} while (addr = next, addr != end);
}

-static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
+static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
phys_addr_t phys, pgprot_t prot,
phys_addr_t (*pgtable_alloc)(int),
int flags)
{
unsigned long next;
- pud_t *pudp;
- p4d_t *p4dp = p4d_offset(pgdp, addr);
p4d_t p4d = READ_ONCE(*p4dp);
+ pud_t *pudp;

if (p4d_none(p4d)) {
p4dval_t p4dval = P4D_TYPE_TABLE | P4D_TABLE_UXN;
@@ -371,6 +370,46 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
pud_clear_fixmap();
}

+static void alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
+ phys_addr_t phys, pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int),
+ int flags)
+{
+ unsigned long next;
+ pgd_t pgd = READ_ONCE(*pgdp);
+ p4d_t *p4dp;
+
+ if (pgd_none(pgd)) {
+ pgdval_t pgdval = PGD_TYPE_TABLE | PGD_TABLE_UXN;
+ phys_addr_t p4d_phys;
+
+ if (flags & NO_EXEC_MAPPINGS)
+ pgdval |= PGD_TABLE_PXN;
+ BUG_ON(!pgtable_alloc);
+ p4d_phys = pgtable_alloc(P4D_SHIFT);
+ __pgd_populate(pgdp, p4d_phys, pgdval);
+ pgd = READ_ONCE(*pgdp);
+ }
+ BUG_ON(pgd_bad(pgd));
+
+ p4dp = p4d_set_fixmap_offset(pgdp, addr);
+ do {
+ p4d_t old_p4d = READ_ONCE(*p4dp);
+
+ next = p4d_addr_end(addr, end);
+
+ alloc_init_pud(p4dp, addr, next, phys, prot,
+ pgtable_alloc, flags);
+
+ BUG_ON(p4d_val(old_p4d) != 0 &&
+ p4d_val(old_p4d) != READ_ONCE(p4d_val(*p4dp)));
+
+ phys += next - addr;
+ } while (p4dp++, addr = next, addr != end);
+
+ p4d_clear_fixmap();
+}
+
static void __create_pgd_mapping_locked(pgd_t *pgdir, phys_addr_t phys,
unsigned long virt, phys_addr_t size,
pgprot_t prot,
@@ -393,7 +432,7 @@ static void __create_pgd_mapping_locked(pgd_t *pgdir, phys_addr_t phys,

do {
next = pgd_addr_end(addr, end);
- alloc_init_pud(pgdp, addr, next, phys, prot, pgtable_alloc,
+ alloc_init_p4d(pgdp, addr, next, phys, prot, pgtable_alloc,
flags);
phys += next - addr;
} while (pgdp++, addr = next, addr != end);
@@ -1120,10 +1159,19 @@ void vmemmap_free(unsigned long start, unsigned long end,
}
#endif /* CONFIG_MEMORY_HOTPLUG */

-static inline pud_t *fixmap_pud(unsigned long addr)
+static inline p4d_t *fixmap_p4d(unsigned long addr)
{
pgd_t *pgdp = pgd_offset_k(addr);
- p4d_t *p4dp = p4d_offset(pgdp, addr);
+ pgd_t pgd = READ_ONCE(*pgdp);
+
+ BUG_ON(pgd_none(pgd) || pgd_bad(pgd));
+
+ return p4d_offset_kimg(pgdp, addr);
+}
+
+static inline pud_t *fixmap_pud(unsigned long addr)
+{
+ p4d_t *p4dp = fixmap_p4d(addr);
p4d_t p4d = READ_ONCE(*p4dp);

BUG_ON(p4d_none(p4d) || p4d_bad(p4d));
@@ -1154,14 +1202,12 @@ static inline pte_t *fixmap_pte(unsigned long addr)
*/
void __init early_fixmap_init(void)
{
- pgd_t *pgdp;
p4d_t *p4dp, p4d;
pud_t *pudp;
pmd_t *pmdp;
unsigned long addr = FIXADDR_START;

- pgdp = pgd_offset_k(addr);
- p4dp = p4d_offset(pgdp, addr);
+ p4dp = fixmap_p4d(addr);
p4d = READ_ONCE(*p4dp);
if (CONFIG_PGTABLE_LEVELS > 3 &&
!(p4d_none(p4d) || p4d_page_paddr(p4d) == __pa_symbol(bm_pud))) {
--
2.39.2