Merge branch 'Rework-sparc32-page-table-layout'

Will Deacon says:

====================
Rework sparc32 page-table layout

This is a reposting of the patch series I sent previously to rework the
sparc32 page-table layout so that 'pmd_t' can be used safely with
READ_ONCE():

https://lore.kernel.org/lkml/20200324104005.11279-1-will@kernel.org

This is blocking the READ_ONCE() rework, which in turn allows us to
bump the minimum GCC version for building the kernel up to 4.8.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/page_32.h

@@ -54,15 +54,15 @@ extern struct sparc_phys_banks sp_banks[SPARC_PHYS_BANKS+1];
  */
 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;
 typedef struct { unsigned long iopgprot; } iopgprot_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)
@@ -82,22 +82,22 @@ typedef struct { unsigned long iopgprot; } iopgprot_t;
  */
 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;
 typedef unsigned long iopgprot_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)
@@ -106,7 +106,7 @@ typedef unsigned long iopgprot_t;
 
 #endif
 
-typedef struct page *pgtable_t;
+typedef pte_t *pgtable_t;
 
 #define TASK_UNMAPPED_BASE	0x50000000
 

arch/sparc/include/asm/pgalloc_32.h

@@ -50,23 +50,24 @@ static inline void free_pmd_fast(pmd_t * pmd)
 #define pmd_free(mm, pmd)		free_pmd_fast(pmd)
 #define __pmd_free_tlb(tlb, pmd, addr)	pmd_free((tlb)->mm, pmd)
 
-void pmd_populate(struct mm_struct *mm, pmd_t *pmdp, struct page *ptep);
-#define pmd_pgtable(pmd) pmd_page(pmd)
+#define pmd_populate(mm, pmd, pte)	pmd_set(pmd, pte)
+#define pmd_pgtable(pmd)		(pgtable_t)__pmd_page(pmd)
 
 void pmd_set(pmd_t *pmdp, pte_t *ptep);
-#define pmd_populate_kernel(MM, PMD, PTE) pmd_set(PMD, PTE)
+#define pmd_populate_kernel		pmd_populate
 
 pgtable_t pte_alloc_one(struct mm_struct *mm);
 
 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

@@ -11,6 +11,16 @@
 
 #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>
 
@@ -34,17 +44,10 @@ unsigned long __init bootmem_init(unsigned long *pages_avail);
 #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)
 
@@ -132,6 +135,17 @@ static inline struct page *pmd_page(pmd_t pmd)
 	return pfn_to_page((pmd_val(pmd) & SRMMU_PTD_PMASK) >> (PAGE_SHIFT-4));
 }
 
+static inline unsigned long __pmd_page(pmd_t pmd)
+{
+	unsigned long v;
+
+	if (srmmu_device_memory(pmd_val(pmd)))
+		BUG();
+
+	v = pmd_val(pmd) & SRMMU_PTD_PMASK;
+	return (unsigned long)__nocache_va(v << 4);
+}
+
 static inline unsigned long pud_page_vaddr(pud_t pud)
 {
 	if (srmmu_device_memory(pud_val(pud))) {
@@ -179,9 +193,7 @@ static inline int pmd_none(pmd_t pmd)
 
 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

@@ -17,39 +17,9 @@
 /* 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		(PTRS_PER_PTE*4)
+#define SRMMU_PMD_TABLE_SIZE		(PTRS_PER_PMD*4)
+#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

@@ -10,6 +10,7 @@
 
 #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.
@@ -227,7 +228,7 @@ static inline unsigned long viking_hwprobe(unsigned long vaddr)
 			     : "=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);
 	}
@@ -237,7 +238,7 @@ static inline unsigned long viking_hwprobe(unsigned long vaddr)
 			     : "=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

@@ -24,7 +24,7 @@
 #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
@@ -273,7 +273,7 @@ not_a_sun4:
 		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
@@ -317,7 +317,7 @@ srmmu_not_viking:
 		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....
@@ -341,7 +341,7 @@ leon_remap:
 		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

@@ -10,6 +10,7 @@
 #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>
 
@@ -293,7 +294,7 @@ hypersparc_flush_tlb_range:
 	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