The patch below does not apply to the 3.0-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From cd94154cc6a28dd9dc271042c1a59c08d26da886 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky <[email protected]> Date: Wed, 11 Apr 2012 14:28:07 +0200 Subject: [PATCH] [S390] fix tlb flushing for page table pages Git commit 36409f6353fc2d7b6516e631415f938eadd92ffa "use generic RCU page-table freeing code" introduced a tlb flushing bug. Partially revert the above git commit and go back to s390 specific page table flush code. For s390 the TLB can contain three types of entries, "normal" TLB page-table entries, TLB combined region-and-segment-table (CRST) entries and real-space entries. Linux does not use real-space entries which leaves normal TLB entries and CRST entries. The CRST entries are intermediate steps in the page-table translation called translation paths. For example a 4K page access in a three-level page table setup will create two CRST TLB entries and one page-table TLB entry. The advantage of that approach is that a page access next to the previous one can reuse the CRST entries and needs just a single read from memory to create the page-table TLB entry. The disadvantage is that the TLB flushing rules are more complicated, before any page-table may be freed the TLB needs to be flushed. In short: the generic RCU page-table freeing code is incorrect for the CRST entries, in particular the check for mm_users < 2 is troublesome. This is applicable to 3.0+ kernels. Cc: <[email protected]> Signed-off-by: Martin Schwidefsky <[email protected]> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 2b7c0fb..9015060 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -90,7 +90,6 @@ config S390 select HAVE_KERNEL_XZ select HAVE_ARCH_MUTEX_CPU_RELAX select HAVE_ARCH_JUMP_LABEL if !MARCH_G5 - select HAVE_RCU_TABLE_FREE if SMP select ARCH_SAVE_PAGE_KEYS if HIBERNATION select HAVE_MEMBLOCK select HAVE_MEMBLOCK_NODE_MAP diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h index 8eef9b5..78e3041 100644 --- a/arch/s390/include/asm/pgalloc.h +++ b/arch/s390/include/asm/pgalloc.h @@ -22,10 +22,7 @@ void crst_table_free(struct mm_struct *, unsigned long *); unsigned long *page_table_alloc(struct mm_struct *, unsigned long); void page_table_free(struct mm_struct *, unsigned long *); -#ifdef CONFIG_HAVE_RCU_TABLE_FREE void page_table_free_rcu(struct mmu_gather *, unsigned long *); -void __tlb_remove_table(void *_table); -#endif static inline void clear_table(unsigned long *s, unsigned long val, size_t n) { diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h index c687a2c..775a5ee 100644 --- a/arch/s390/include/asm/tlb.h +++ b/arch/s390/include/asm/tlb.h @@ -30,14 +30,10 @@ struct mmu_gather { struct mm_struct *mm; -#ifdef CONFIG_HAVE_RCU_TABLE_FREE struct mmu_table_batch *batch; -#endif unsigned int fullmm; - unsigned int need_flush; }; -#ifdef CONFIG_HAVE_RCU_TABLE_FREE struct mmu_table_batch { struct rcu_head rcu; unsigned int nr; @@ -49,7 +45,6 @@ struct mmu_table_batch { extern void tlb_table_flush(struct mmu_gather *tlb); extern void tlb_remove_table(struct mmu_gather *tlb, void *table); -#endif static inline void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, @@ -57,29 +52,20 @@ static inline void tlb_gather_mmu(struct mmu_gather *tlb, { tlb->mm = mm; tlb->fullmm = full_mm_flush; - tlb->need_flush = 0; -#ifdef CONFIG_HAVE_RCU_TABLE_FREE tlb->batch = NULL; -#endif if (tlb->fullmm) __tlb_flush_mm(mm); } static inline void tlb_flush_mmu(struct mmu_gather *tlb) { - if (!tlb->need_flush) - return; - tlb->need_flush = 0; - __tlb_flush_mm(tlb->mm); -#ifdef CONFIG_HAVE_RCU_TABLE_FREE tlb_table_flush(tlb); -#endif } static inline void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end) { - tlb_flush_mmu(tlb); + tlb_table_flush(tlb); } /* @@ -105,10 +91,8 @@ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page) static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, unsigned long address) { -#ifdef CONFIG_HAVE_RCU_TABLE_FREE if (!tlb->fullmm) return page_table_free_rcu(tlb, (unsigned long *) pte); -#endif page_table_free(tlb->mm, (unsigned long *) pte); } @@ -125,10 +109,8 @@ static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, #ifdef __s390x__ if (tlb->mm->context.asce_limit <= (1UL << 31)) return; -#ifdef CONFIG_HAVE_RCU_TABLE_FREE if (!tlb->fullmm) return tlb_remove_table(tlb, pmd); -#endif crst_table_free(tlb->mm, (unsigned long *) pmd); #endif } @@ -146,10 +128,8 @@ static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud, #ifdef __s390x__ if (tlb->mm->context.asce_limit <= (1UL << 42)) return; -#ifdef CONFIG_HAVE_RCU_TABLE_FREE if (!tlb->fullmm) return tlb_remove_table(tlb, pud); -#endif crst_table_free(tlb->mm, (unsigned long *) pud); #endif } diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 373adf6..6e765bf 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -678,8 +678,6 @@ void page_table_free(struct mm_struct *mm, unsigned long *table) } } -#ifdef CONFIG_HAVE_RCU_TABLE_FREE - static void __page_table_free_rcu(void *table, unsigned bit) { struct page *page; @@ -733,7 +731,66 @@ void __tlb_remove_table(void *_table) free_pages((unsigned long) table, ALLOC_ORDER); } -#endif +static void tlb_remove_table_smp_sync(void *arg) +{ + /* Simply deliver the interrupt */ +} + +static void tlb_remove_table_one(void *table) +{ + /* + * This isn't an RCU grace period and hence the page-tables cannot be + * assumed to be actually RCU-freed. + * + * It is however sufficient for software page-table walkers that rely + * on IRQ disabling. See the comment near struct mmu_table_batch. + */ + smp_call_function(tlb_remove_table_smp_sync, NULL, 1); + __tlb_remove_table(table); +} + +static void tlb_remove_table_rcu(struct rcu_head *head) +{ + struct mmu_table_batch *batch; + int i; + + batch = container_of(head, struct mmu_table_batch, rcu); + + for (i = 0; i < batch->nr; i++) + __tlb_remove_table(batch->tables[i]); + + free_page((unsigned long)batch); +} + +void tlb_table_flush(struct mmu_gather *tlb) +{ + struct mmu_table_batch **batch = &tlb->batch; + + if (*batch) { + __tlb_flush_mm(tlb->mm); + call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); + *batch = NULL; + } +} + +void tlb_remove_table(struct mmu_gather *tlb, void *table) +{ + struct mmu_table_batch **batch = &tlb->batch; + + if (*batch == NULL) { + *batch = (struct mmu_table_batch *) + __get_free_page(GFP_NOWAIT | __GFP_NOWARN); + if (*batch == NULL) { + __tlb_flush_mm(tlb->mm); + tlb_remove_table_one(table); + return; + } + (*batch)->nr = 0; + } + (*batch)->tables[(*batch)->nr++] = table; + if ((*batch)->nr == MAX_TABLE_BATCH) + tlb_table_flush(tlb); +} /* * switch on pgstes for its userspace process (for kvm) -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
