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Subject[PATCH 13/17] mips/tlb: Fix __p*_free_tlb()
Just like regular pages, page directories need to observe the
following order:

1) unhook
2) TLB invalidate
3) free

to ensure it is safe against concurrent accesses.

MIPS has (thanks to Paul Burton for setting me straight):

- HAVE_FAST_GUP, which means we need to consider software
walkers (many MIPS also have software TLB-fill, which is a similar
software walker).

- non-page, page directories, which requires a custom table free.

- Mostly IPI-based TLB invalidate, but it wouldn't be MIPS if it
didn't also have broadcast TLB invalidate (I6500, GINVT).

This means that in generic MIPS needs HAVE_RCU_TABLE_FREE.

Cc: Paul Burton <paul.burton@mips.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/mips/Kconfig | 1 +
arch/mips/include/asm/pgalloc.h | 13 ++++++-------
arch/mips/mm/pgtable.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 41 insertions(+), 7 deletions(-)

--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -57,6 +57,7 @@ config MIPS
select HAVE_DYNAMIC_FTRACE
select HAVE_EXIT_THREAD
select HAVE_FAST_GUP
+ select MMU_GATHER_RCU_TABLE_FREE
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -41,6 +41,9 @@ static inline void pud_populate(struct m
}
#endif

+extern void __tlb_remove_table(void *table);
+extern void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int idx);
+
/*
* Initialize a new pgd / pmd table with invalid pointers.
*/
@@ -52,11 +55,7 @@ static inline void pgd_free(struct mm_st
free_pages((unsigned long)pgd, PGD_ORDER);
}

-#define __pte_free_tlb(tlb,pte,address) \
-do { \
- pgtable_pte_page_dtor(pte); \
- tlb_remove_page((tlb), pte); \
-} while (0)
+#define __pte_free_tlb(tlb,pte,address) pgtable_free_tlb((tlb), (pte), 0)

#ifndef __PAGETABLE_PMD_FOLDED

@@ -75,7 +74,7 @@ static inline void pmd_free(struct mm_st
free_pages((unsigned long)pmd, PMD_ORDER);
}

-#define __pmd_free_tlb(tlb, x, addr) pmd_free((tlb)->mm, x)
+#define __pmd_free_tlb(tlb, x, addr) pgtable_free_tlb((tlb), (x), 1)

#endif

@@ -101,7 +100,7 @@ static inline void p4d_populate(struct m
set_p4d(p4d, __p4d((unsigned long)pud));
}

-#define __pud_free_tlb(tlb, x, addr) pud_free((tlb)->mm, x)
+#define __pud_free_tlb(tlb, x, addr) pgtable_free_tlb((tlb), (x), 2)

#endif /* __PAGETABLE_PUD_FOLDED */

--- a/arch/mips/mm/pgtable.c
+++ b/arch/mips/mm/pgtable.c
@@ -7,6 +7,7 @@
#include <linux/mm.h>
#include <linux/string.h>
#include <asm/pgalloc.h>
+#include <asm-generic/tlb.h>

pgd_t *pgd_alloc(struct mm_struct *mm)
{
@@ -23,3 +24,36 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
return ret;
}
EXPORT_SYMBOL_GPL(pgd_alloc);
+
+#define TLB_IDX_MASK 0x3
+
+void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int idx)
+{
+ unsigned long pgf = (unsigned long)table;
+ BUG_ON(idx > TLB_IDX_MASK);
+ BUG_ON(pgf & TLB_IDX_MASK);
+ pgf |= idx;
+ tlb_remove_table(tlb, (void *)pgf);
+}
+
+void __tlb_remove_table(void *table)
+{
+ void *dir = (void *)((unsigned long)table & ~TLB_IDX_MASK);
+ int idx = (unsigned long)table & TLB_IDX_MASK;
+
+ switch (idx) {
+#ifndef __PAGETABLE_PUD_FOLDED
+ case 2: /* PUD */
+ pud_free(NULL, dir);
+ break;
+#endif
+#ifndef __PAGETABLE_PMD_FOLDED
+ case 1: /* PMD */
+ pmd_free(NULL, dir);
+ break;
+#endif
+ case 0: /* PTE */
+ pte_free(NULL, dir);
+ break;
+ }
+}

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