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" <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

arch/sparc/include/asm/page_32.h

···
  */
 typedef struct { unsigned long pte; } pte_t;
 typedef struct { unsigned long iopte; } iopte_t;
-typedef struct { unsigned long pmdv[16]; } pmd_t;
+typedef struct { unsigned long pmd; } pmd_t;
 typedef struct { unsigned long pgd; } pgd_t;
 typedef struct { unsigned long ctxd; } ctxd_t;
 typedef struct { unsigned long pgprot; } pgprot_t;
···
 
 #define pte_val(x)	((x).pte)
 #define iopte_val(x)	((x).iopte)
-#define pmd_val(x)      ((x).pmdv[0])
+#define pmd_val(x)      ((x).pmd)
 #define pgd_val(x)	((x).pgd)
 #define ctxd_val(x)	((x).ctxd)
 #define pgprot_val(x)	((x).pgprot)
···
  */
 typedef unsigned long pte_t;
 typedef unsigned long iopte_t;
-typedef struct { unsigned long pmdv[16]; } pmd_t;
+typedef unsigned long pmd_t;
 typedef unsigned long pgd_t;
 typedef unsigned long ctxd_t;
 typedef unsigned long pgprot_t;
···
 
 #define pte_val(x)	(x)
 #define iopte_val(x)	(x)
-#define pmd_val(x)      ((x).pmdv[0])
+#define pmd_val(x)      (x)
 #define pgd_val(x)	(x)
 #define ctxd_val(x)	(x)
 #define pgprot_val(x)	(x)
 #define iopgprot_val(x)	(x)
 
 #define __pte(x)	(x)
-#define __pmd(x)	((pmd_t) { { (x) }, })
+#define __pmd(x)	(x)
 #define __iopte(x)	(x)
 #define __pgd(x)	(x)
 #define __ctxd(x)	(x)

arch/sparc/include/asm/pgalloc_32.h

···
 
 static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
 {
-	return srmmu_get_nocache(PTE_SIZE, PTE_SIZE);
+	return srmmu_get_nocache(SRMMU_PTE_TABLE_SIZE,
+				 SRMMU_PTE_TABLE_SIZE);
 }
 
 
 static inline void free_pte_fast(pte_t *pte)
 {
-	srmmu_free_nocache(pte, PTE_SIZE);
+	srmmu_free_nocache(pte, SRMMU_PTE_TABLE_SIZE);
 }
 
 #define pte_free_kernel(mm, pte)	free_pte_fast(pte)

arch/sparc/include/asm/pgtable_32.h

···
 
 #include <linux/const.h>
 
+#define PMD_SHIFT		18
+#define PMD_SIZE        	(1UL << PMD_SHIFT)
+#define PMD_MASK        	(~(PMD_SIZE-1))
+#define PMD_ALIGN(__addr) 	(((__addr) + ~PMD_MASK) & PMD_MASK)
+
+#define PGDIR_SHIFT     	24
+#define PGDIR_SIZE      	(1UL << PGDIR_SHIFT)
+#define PGDIR_MASK      	(~(PGDIR_SIZE-1))
+#define PGDIR_ALIGN(__addr) 	(((__addr) + ~PGDIR_MASK) & PGDIR_MASK)
+
 #ifndef __ASSEMBLY__
 #include <asm-generic/pgtable-nopud.h>
 
···
 #define pmd_ERROR(e)   __builtin_trap()
 #define pgd_ERROR(e)   __builtin_trap()
 
-#define PMD_SHIFT		22
-#define PMD_SIZE        	(1UL << PMD_SHIFT)
-#define PMD_MASK        	(~(PMD_SIZE-1))
-#define PMD_ALIGN(__addr) 	(((__addr) + ~PMD_MASK) & PMD_MASK)
-#define PGDIR_SHIFT     	SRMMU_PGDIR_SHIFT
-#define PGDIR_SIZE      	SRMMU_PGDIR_SIZE
-#define PGDIR_MASK      	SRMMU_PGDIR_MASK
-#define PTRS_PER_PTE    	1024
-#define PTRS_PER_PMD    	SRMMU_PTRS_PER_PMD
-#define PTRS_PER_PGD    	SRMMU_PTRS_PER_PGD
-#define USER_PTRS_PER_PGD	PAGE_OFFSET / SRMMU_PGDIR_SIZE
+#define PTRS_PER_PTE    	64
+#define PTRS_PER_PMD    	64
+#define PTRS_PER_PGD    	256
+#define USER_PTRS_PER_PGD	PAGE_OFFSET / PGDIR_SIZE
 #define FIRST_USER_ADDRESS	0UL
 #define PTE_SIZE		(PTRS_PER_PTE*4)
 
···
 
 static inline void pmd_clear(pmd_t *pmdp)
 {
-	int i;
-	for (i = 0; i < PTRS_PER_PTE/SRMMU_REAL_PTRS_PER_PTE; i++)
-		set_pte((pte_t *)&pmdp->pmdv[i], __pte(0));
+	set_pte((pte_t *)&pmd_val(*pmdp), __pte(0));
 }
 
 static inline int pud_none(pud_t pud)

arch/sparc/include/asm/pgtsrmmu.h

···
 /* Number of contexts is implementation-dependent; 64k is the most we support */
 #define SRMMU_MAX_CONTEXTS	65536
 
-/* PMD_SHIFT determines the size of the area a second-level page table entry can map */
-#define SRMMU_REAL_PMD_SHIFT		18
-#define SRMMU_REAL_PMD_SIZE		(1UL << SRMMU_REAL_PMD_SHIFT)
-#define SRMMU_REAL_PMD_MASK		(~(SRMMU_REAL_PMD_SIZE-1))
-#define SRMMU_REAL_PMD_ALIGN(__addr)	(((__addr)+SRMMU_REAL_PMD_SIZE-1)&SRMMU_REAL_PMD_MASK)
-
-/* PGDIR_SHIFT determines what a third-level page table entry can map */
-#define SRMMU_PGDIR_SHIFT       24
-#define SRMMU_PGDIR_SIZE        (1UL << SRMMU_PGDIR_SHIFT)
-#define SRMMU_PGDIR_MASK        (~(SRMMU_PGDIR_SIZE-1))
-#define SRMMU_PGDIR_ALIGN(addr) (((addr)+SRMMU_PGDIR_SIZE-1)&SRMMU_PGDIR_MASK)
-
-#define SRMMU_REAL_PTRS_PER_PTE	64
-#define SRMMU_REAL_PTRS_PER_PMD	64
-#define SRMMU_PTRS_PER_PGD	256
-
-#define SRMMU_REAL_PTE_TABLE_SIZE	(SRMMU_REAL_PTRS_PER_PTE*4)
-#define SRMMU_PMD_TABLE_SIZE		(SRMMU_REAL_PTRS_PER_PMD*4)
-#define SRMMU_PGD_TABLE_SIZE		(SRMMU_PTRS_PER_PGD*4)
-
-/*
- * To support pagetables in highmem, Linux introduces APIs which
- * return struct page* and generally manipulate page tables when
- * they are not mapped into kernel space. Our hardware page tables
- * are smaller than pages. We lump hardware tabes into big, page sized
- * software tables.
- *
- * PMD_SHIFT determines the size of the area a second-level page table entry
- * can map, and our pmd_t is 16 times larger than normal.  The values which
- * were once defined here are now generic for 4c and srmmu, so they're
- * found in pgtable.h.
- */
-#define SRMMU_PTRS_PER_PMD	4
+#define SRMMU_PTE_TABLE_SIZE		(PAGE_SIZE)
+#define SRMMU_PMD_TABLE_SIZE		(PAGE_SIZE)
+#define SRMMU_PGD_TABLE_SIZE		(PTRS_PER_PGD*4)
 
 /* Definition of the values in the ET field of PTD's and PTE's */
 #define SRMMU_ET_MASK         0x3

arch/sparc/include/asm/viking.h

···
 
 #include <asm/asi.h>
 #include <asm/mxcc.h>
+#include <asm/pgtable.h>
 #include <asm/pgtsrmmu.h>
 
 /* Bits in the SRMMU control register for GNU/Viking modules.
···
 			     : "=r" (val)
 			     : "r" (vaddr | 0x200), "i" (ASI_M_FLUSH_PROBE));
 	if ((val & SRMMU_ET_MASK) == SRMMU_ET_PTE) {
-		vaddr &= ~SRMMU_PGDIR_MASK;
+		vaddr &= ~PGDIR_MASK;
 		vaddr >>= PAGE_SHIFT;
 		return val | (vaddr << 8);
 	}
···
 			     : "=r" (val)
 			     : "r" (vaddr | 0x100), "i" (ASI_M_FLUSH_PROBE));
 	if ((val & SRMMU_ET_MASK) == SRMMU_ET_PTE) {
-		vaddr &= ~SRMMU_REAL_PMD_MASK;
+		vaddr &= ~PMD_MASK;
 		vaddr >>= PAGE_SHIFT;
 		return val | (vaddr << 8);
 	}

arch/sparc/kernel/head_32.S

···
 #include <asm/winmacro.h>
 #include <asm/thread_info.h>	/* TI_UWINMASK */
 #include <asm/errno.h>
-#include <asm/pgtsrmmu.h>	/* SRMMU_PGDIR_SHIFT */
+#include <asm/pgtable.h>	/* PGDIR_SHIFT */
 #include <asm/export.h>
 
 	.data
···
 		lda	[%o1] ASI_M_BYPASS, %o2		! This is the 0x0 16MB pgd
 
 		/* Calculate to KERNBASE entry. */
-		add	%o1, KERNBASE >> (SRMMU_PGDIR_SHIFT - 2), %o3
+		add	%o1, KERNBASE >> (PGDIR_SHIFT - 2), %o3
 
 		/* Poke the entry into the calculated address. */
 		sta	%o2, [%o3] ASI_M_BYPASS
···
 		sll	%g1, 0x8, %g1			! make phys addr for l1 tbl
 
 		lda	[%g1] ASI_M_BYPASS, %g2		! get level1 entry for 0x0
-		add	%g1, KERNBASE >> (SRMMU_PGDIR_SHIFT - 2), %g3
+		add	%g1, KERNBASE >> (PGDIR_SHIFT - 2), %g3
 		sta	%g2, [%g3] ASI_M_BYPASS		! place at KERNBASE entry
 		b	go_to_highmem
 		 nop					! wheee....
···
 		sll	%g1, 0x8, %g1			! make phys addr for l1 tbl
 
 		lda	[%g1] ASI_M_BYPASS, %g2		! get level1 entry for 0x0
-		add	%g1, KERNBASE >> (SRMMU_PGDIR_SHIFT - 2), %g3
+		add	%g1, KERNBASE >> (PGDIR_SHIFT - 2), %g3
 		sta	%g2, [%g3] ASI_M_BYPASS		! place at KERNBASE entry
 		b	go_to_highmem
 		 nop					! wheee....

arch/sparc/mm/hypersparc.S

···
 #include <asm/asm-offsets.h>
 #include <asm/asi.h>
 #include <asm/page.h>
+#include <asm/pgtable.h>
 #include <asm/pgtsrmmu.h>
 #include <linux/init.h>
 
···
 	cmp	%o3, -1
 	be	hypersparc_flush_tlb_range_out
 #endif
-	 sethi	%hi(~((1 << SRMMU_PGDIR_SHIFT) - 1)), %o4
+	 sethi	%hi(~((1 << PGDIR_SHIFT) - 1)), %o4
 	sta	%o3, [%g1] ASI_M_MMUREGS
 	and	%o1, %o4, %o1
 	add	%o1, 0x200, %o1

arch/sparc/mm/srmmu.c

···
 
 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.. */
···
 {
 	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));
 }
···
 	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 */
···
 		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;
 		}
 
···
 		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))) {
···
 			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)
 				early_pgtable_allocfail("pte");
 			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);
···
 /* 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;
···
 
 	while (vstart < vend) {
 		do_large_mapping(vstart, pstart);
-		vstart += SRMMU_PGDIR_SIZE; pstart += SRMMU_PGDIR_SIZE;
+		vstart += PGDIR_SIZE; pstart += PGDIR_SIZE;
 	}
 	return vstart;
 }

arch/sparc/mm/viking.S

···
 #include <asm/asi.h>
 #include <asm/mxcc.h>
 #include <asm/page.h>
+#include <asm/pgtable.h>
 #include <asm/pgtsrmmu.h>
 #include <asm/viking.h>
 
···
 	cmp	%o3, -1
 	be	2f
 #endif
-	sethi	%hi(~((1 << SRMMU_PGDIR_SHIFT) - 1)), %o4
+	sethi	%hi(~((1 << PGDIR_SHIFT) - 1)), %o4
 	sta	%o3, [%g1] ASI_M_MMUREGS
 	and	%o1, %o4, %o1
 	add	%o1, 0x200, %o1
···
 	ld	[%o0 + VMA_VM_MM], %o0
 	ld	[%o0 + AOFF_mm_context], %o3
 	lda	[%g1] ASI_M_MMUREGS, %g5
-	sethi	%hi(~((1 << SRMMU_PGDIR_SHIFT) - 1)), %o4
+	sethi	%hi(~((1 << PGDIR_SHIFT) - 1)), %o4
 	sta	%o3, [%g1] ASI_M_MMUREGS
 	and	%o1, %o4, %o1
 	add	%o1, 0x200, %o1