MIPS: Add 48-bit VA space (and 4-level page tables) for 4K pages.

Some users must have 4K pages while needing a 48-bit VA space size.
The cleanest way do do this is to go to a 4-level page table for this
case.  Each page table level using order-0 pages adds 9 bits to the
VA size (at 4K pages, so for four levels we get 9 * 4 + 12 == 48-bits.

For the 4K page size case only we add support functions for the PUD
level of the page table tree, also the TLB exception handlers get an
extra level of tree walk.

[david.daney@cavium.com: Forward port to v4.10.]
[david.daney@cavium.com: Forward port to v4.11.]

Signed-off-by: Alex Belits <alex.belits@cavium.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Alex Belits <alex.belits@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15312/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 55 insertions, 3 deletions

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index aa75849c36bc..37aa931501bf 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -537,6 +537,9 @@ unsigned long pgd_current[NR_CPUS];
  * it in the linker script.
  */
 pgd_t swapper_pg_dir[_PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
+#ifndef __PAGETABLE_PUD_FOLDED
+pud_t invalid_pud_table[PTRS_PER_PUD] __page_aligned_bss;
+#endif
 #ifndef __PAGETABLE_PMD_FOLDED
 pmd_t invalid_pmd_table[PTRS_PER_PMD] __page_aligned_bss;
 EXPORT_SYMBOL_GPL(invalid_pmd_table);
diff --git a/arch/mips/mm/pgtable-64.c b/arch/mips/mm/pgtable-64.c
index 0ae7b28b4db5..6fd6e96fdebb 100644
--- a/arch/mips/mm/pgtable-64.c
+++ b/arch/mips/mm/pgtable-64.c
@@ -19,10 +19,12 @@ void pgd_init(unsigned long page)
 	unsigned long *p, *end;
 	unsigned long entry;
 
-#ifdef __PAGETABLE_PMD_FOLDED
-	entry = (unsigned long)invalid_pte_table;
-#else
+#if !defined(__PAGETABLE_PUD_FOLDED)
+	entry = (unsigned long)invalid_pud_table;
+#elif !defined(__PAGETABLE_PMD_FOLDED)
 	entry = (unsigned long)invalid_pmd_table;
+#else
+	entry = (unsigned long)invalid_pte_table;
 #endif
 
 	p = (unsigned long *) page;
@@ -64,6 +66,28 @@ void pmd_init(unsigned long addr, unsigned long pagetable)
 EXPORT_SYMBOL_GPL(pmd_init);
 #endif
 
+#ifndef __PAGETABLE_PUD_FOLDED
+void pud_init(unsigned long addr, unsigned long pagetable)
+{
+	unsigned long *p, *end;
+
+	p = (unsigned long *)addr;
+	end = p + PTRS_PER_PUD;
+
+	do {
+		p[0] = pagetable;
+		p[1] = pagetable;
+		p[2] = pagetable;
+		p[3] = pagetable;
+		p[4] = pagetable;
+		p += 8;
+		p[-3] = pagetable;
+		p[-2] = pagetable;
+		p[-1] = pagetable;
+	} while (p != end);
+}
+#endif
+
 pmd_t mk_pmd(struct page *page, pgprot_t prot)
 {
 	pmd_t pmd;
@@ -87,6 +111,9 @@ void __init pagetable_init(void)
 
 	/* Initialize the entire pgd.  */
 	pgd_init((unsigned long)swapper_pg_dir);
+#ifndef __PAGETABLE_PUD_FOLDED
+	pud_init((unsigned long)invalid_pud_table, (unsigned long)invalid_pmd_table);
+#endif
 #ifndef __PAGETABLE_PMD_FOLDED
 	pmd_init((unsigned long)invalid_pmd_table, (unsigned long)invalid_pte_table);
 #endif
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 4f642e07c2b1..ed1c5297547a 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -865,6 +865,13 @@ void build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
 
 	uasm_i_andi(p, tmp, tmp, (PTRS_PER_PGD - 1)<<3);
 	uasm_i_daddu(p, ptr, ptr, tmp); /* add in pgd offset */
+#ifndef __PAGETABLE_PUD_FOLDED
+	uasm_i_dmfc0(p, tmp, C0_BADVADDR); /* get faulting address */
+	uasm_i_ld(p, ptr, 0, ptr); /* get pud pointer */
+	uasm_i_dsrl_safe(p, tmp, tmp, PUD_SHIFT - 3); /* get pud offset in bytes */
+	uasm_i_andi(p, tmp, tmp, (PTRS_PER_PUD - 1) << 3);
+	uasm_i_daddu(p, ptr, ptr, tmp); /* add in pud offset */
+#endif
 #ifndef __PAGETABLE_PMD_FOLDED
 	uasm_i_dmfc0(p, tmp, C0_BADVADDR); /* get faulting address */
 	uasm_i_ld(p, ptr, 0, ptr); /* get pmd pointer */
@@ -1184,6 +1191,21 @@ build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
 		uasm_i_ld(p, LOC_PTEP, 0, ptr); /* get pmd pointer */
 	}
 
+#ifndef __PAGETABLE_PUD_FOLDED
+	/* get pud offset in bytes */
+	uasm_i_dsrl_safe(p, scratch, tmp, PUD_SHIFT - 3);
+	uasm_i_andi(p, scratch, scratch, (PTRS_PER_PUD - 1) << 3);
+
+	if (use_lwx_insns()) {
+		UASM_i_LWX(p, ptr, scratch, ptr);
+	} else {
+		uasm_i_daddu(p, ptr, ptr, scratch); /* add in pmd offset */
+		UASM_i_LW(p, ptr, 0, ptr);
+	}
+	/* ptr contains a pointer to PMD entry */
+	/* tmp contains the address */
+#endif
+
 #ifndef __PAGETABLE_PMD_FOLDED
 	/* get pmd offset in bytes */
 	uasm_i_dsrl_safe(p, scratch, tmp, PMD_SHIFT - 3);