sparc32: mm: Restructure sparc32 MMU page-table layout

The "SRMMU" supports 4k pages using a fixed three-level walk with a
256-entry PGD and 64-entry PMD/PTE levels. In order to fill a page
with a 'pgtable_t', the SRMMU code allocates four native PTE tables
into a single PTE allocation and similarly for the PMD level, leading
to an array of 16 physical pointers in a 'pmd_t'

This breaks the generic code which assumes READ_ONCE(*pmd) will be
word sized.

In a manner similar to ef22d8abd876 ("m68k: mm: Restructure Motorola
MMU page-table layout"), this patch implements the native page-table
setup directly. This significantly increases the page-table memory
overhead, but will be addresses in a subsequent patch.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 40 deletions

diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index cb9ded8a68b7..50da4bcdd6fa 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -136,26 +136,14 @@ static void msi_set_sync(void)
 
 void pmd_set(pmd_t *pmdp, pte_t *ptep)
 {
-	unsigned long ptp;	/* Physical address, shifted right by 4 */
-	int i;
-
-	ptp = __nocache_pa(ptep) >> 4;
-	for (i = 0; i < PTRS_PER_PTE/SRMMU_REAL_PTRS_PER_PTE; i++) {
-		set_pte((pte_t *)&pmdp->pmdv[i], __pte(SRMMU_ET_PTD | ptp));
-		ptp += (SRMMU_REAL_PTRS_PER_PTE * sizeof(pte_t) >> 4);
-	}
+	unsigned long ptp = __nocache_pa(ptep) >> 4;
+	set_pte((pte_t *)&pmd_val(*pmdp), __pte(SRMMU_ET_PTD | ptp));
 }
 
 void pmd_populate(struct mm_struct *mm, pmd_t *pmdp, struct page *ptep)
 {
-	unsigned long ptp;	/* Physical address, shifted right by 4 */
-	int i;
-
-	ptp = page_to_pfn(ptep) << (PAGE_SHIFT-4);	/* watch for overflow */
-	for (i = 0; i < PTRS_PER_PTE/SRMMU_REAL_PTRS_PER_PTE; i++) {
-		set_pte((pte_t *)&pmdp->pmdv[i], __pte(SRMMU_ET_PTD | ptp));
-		ptp += (SRMMU_REAL_PTRS_PER_PTE * sizeof(pte_t) >> 4);
-	}
+	unsigned long ptp = page_to_pfn(ptep) << (PAGE_SHIFT-4); /* watch for overflow */
+	set_pte((pte_t *)&pmd_val(*pmdp), __pte(SRMMU_ET_PTD | ptp));
 }
 
 /* Find an entry in the third-level page table.. */
@@ -163,7 +151,7 @@ pte_t *pte_offset_kernel(pmd_t *dir, unsigned long address)
 {
 	void *pte;
 
-	pte = __nocache_va((dir->pmdv[0] & SRMMU_PTD_PMASK) << 4);
+	pte = __nocache_va((pmd_val(*dir) & SRMMU_PTD_PMASK) << 4);
 	return (pte_t *) pte +
 	    ((address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1));
 }
@@ -400,7 +388,7 @@ void pte_free(struct mm_struct *mm, pgtable_t pte)
 	p = page_to_pfn(pte) << PAGE_SHIFT;	/* Physical address */
 
 	/* free non cached virtual address*/
-	srmmu_free_nocache(__nocache_va(p), PTE_SIZE);
+	srmmu_free_nocache(__nocache_va(p), SRMMU_PTE_TABLE_SIZE);
 }
 
 /* context handling - a dynamically sized pool is used */
@@ -822,13 +810,13 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
 		what = 0;
 		addr = start - PAGE_SIZE;
 
-		if (!(start & ~(SRMMU_REAL_PMD_MASK))) {
-			if (srmmu_probe(addr + SRMMU_REAL_PMD_SIZE) == probed)
+		if (!(start & ~(PMD_MASK))) {
+			if (srmmu_probe(addr + PMD_SIZE) == probed)
 				what = 1;
 		}
 
-		if (!(start & ~(SRMMU_PGDIR_MASK))) {
-			if (srmmu_probe(addr + SRMMU_PGDIR_SIZE) == probed)
+		if (!(start & ~(PGDIR_MASK))) {
+			if (srmmu_probe(addr + PGDIR_SIZE) == probed)
 				what = 2;
 		}
 
@@ -837,7 +825,7 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
 		pudp = pud_offset(p4dp, start);
 		if (what == 2) {
 			*(pgd_t *)__nocache_fix(pgdp) = __pgd(probed);
-			start += SRMMU_PGDIR_SIZE;
+			start += PGDIR_SIZE;
 			continue;
 		}
 		if (pud_none(*(pud_t *)__nocache_fix(pudp))) {
@@ -849,6 +837,11 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
 			pud_set(__nocache_fix(pudp), pmdp);
 		}
 		pmdp = pmd_offset(__nocache_fix(pgdp), start);
+		if (what == 1) {
+			*(pmd_t *)__nocache_fix(pmdp) = __pmd(probed);
+			start += PMD_SIZE;
+			continue;
+		}
 		if (srmmu_pmd_none(*(pmd_t *)__nocache_fix(pmdp))) {
 			ptep = __srmmu_get_nocache(PTE_SIZE, PTE_SIZE);
 			if (ptep == NULL)
@@ -856,19 +849,6 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
 			memset(__nocache_fix(ptep), 0, PTE_SIZE);
 			pmd_set(__nocache_fix(pmdp), ptep);
 		}
-		if (what == 1) {
-			/* We bend the rule where all 16 PTPs in a pmd_t point
-			 * inside the same PTE page, and we leak a perfectly
-			 * good hardware PTE piece. Alternatives seem worse.
-			 */
-			unsigned int x;	/* Index of HW PMD in soft cluster */
-			unsigned long *val;
-			x = (start >> PMD_SHIFT) & 15;
-			val = &pmdp->pmdv[x];
-			*(unsigned long *)__nocache_fix(val) = probed;
-			start += SRMMU_REAL_PMD_SIZE;
-			continue;
-		}
 		ptep = pte_offset_kernel(__nocache_fix(pmdp), start);
 		*(pte_t *)__nocache_fix(ptep) = __pte(probed);
 		start += PAGE_SIZE;
@@ -890,9 +870,9 @@ static void __init do_large_mapping(unsigned long vaddr, unsigned long phys_base
 /* Map sp_bank entry SP_ENTRY, starting at virtual address VBASE. */
 static unsigned long __init map_spbank(unsigned long vbase, int sp_entry)
 {
-	unsigned long pstart = (sp_banks[sp_entry].base_addr & SRMMU_PGDIR_MASK);
-	unsigned long vstart = (vbase & SRMMU_PGDIR_MASK);
-	unsigned long vend = SRMMU_PGDIR_ALIGN(vbase + sp_banks[sp_entry].num_bytes);
+	unsigned long pstart = (sp_banks[sp_entry].base_addr & PGDIR_MASK);
+	unsigned long vstart = (vbase & PGDIR_MASK);
+	unsigned long vend = PGDIR_ALIGN(vbase + sp_banks[sp_entry].num_bytes);
 	/* Map "low" memory only */
 	const unsigned long min_vaddr = PAGE_OFFSET;
 	const unsigned long max_vaddr = PAGE_OFFSET + SRMMU_MAXMEM;
@@ -905,7 +885,7 @@ static unsigned long __init map_spbank(unsigned long vbase, int sp_entry)
 
 	while (vstart < vend) {
 		do_large_mapping(vstart, pstart);
-		vstart += SRMMU_PGDIR_SIZE; pstart += SRMMU_PGDIR_SIZE;
+		vstart += PGDIR_SIZE; pstart += PGDIR_SIZE;
 	}
 	return vstart;
 }