From ed4cbc81addbc076b016c5b979fd1a02f0897f0a Mon Sep 17 00:00:00 2001 From: Markos Chandras Date: Mon, 26 Jan 2015 13:04:33 +0000 Subject: [PATCH] MIPS: HTW: Prevent accidental HTW start due to nested htw_{start, stop} activate_mm() and switch_mm() call get_new_mmu_context() which in turn can enable the HTW before the entryhi is changed with the new ASID. Since the latter will enable the HTW in local_flush_tlb_all(), then there is a small timing window where the HTW is running with the new ASID but with an old pgd since the TLBMISS_HANDLER_SETUP_PGD hasn't assigned a new one yet. In order to prevent that, we introduce a simple htw counter to avoid starting HTW accidentally due to nested htw_{start,stop}() sequences. Moreover, since various IPI calls can enforce TLB flushing operations on a different core, such an operation may interrupt another htw_{stop,start} in progress leading inconsistent updates of the htw_seq variable. In order to avoid that, we disable the interrupts whenever we update that variable. Signed-off-by: Markos Chandras Cc: # 3.17+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9118/ Signed-off-by: Ralf Baechle --- arch/mips/include/asm/cpu-info.h | 5 +++++ arch/mips/include/asm/mmu_context.h | 7 ++++++- arch/mips/include/asm/pgtable.h | 24 ++++++++++++++++++------ arch/mips/kernel/cpu-probe.c | 4 +++- 4 files changed, 32 insertions(+), 8 deletions(-) diff --git a/arch/mips/include/asm/cpu-info.h b/arch/mips/include/asm/cpu-info.h index a6c9ccb..c3f4f2d 100644 --- a/arch/mips/include/asm/cpu-info.h +++ b/arch/mips/include/asm/cpu-info.h @@ -84,6 +84,11 @@ struct cpuinfo_mips { * (shifted by _CACHE_SHIFT) */ unsigned int writecombine; + /* + * Simple counter to prevent enabling HTW in nested + * htw_start/htw_stop calls + */ + unsigned int htw_seq; } __attribute__((aligned(SMP_CACHE_BYTES))); extern struct cpuinfo_mips cpu_data[]; diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h index 87f1107..45914b5 100644 --- a/arch/mips/include/asm/mmu_context.h +++ b/arch/mips/include/asm/mmu_context.h @@ -25,7 +25,6 @@ do { \ if (cpu_has_htw) { \ write_c0_pwbase(pgd); \ back_to_back_c0_hazard(); \ - htw_reset(); \ } \ } while (0) @@ -144,6 +143,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, unsigned long flags; local_irq_save(flags); + htw_stop(); /* Check if our ASID is of an older version and thus invalid */ if ((cpu_context(cpu, next) ^ asid_cache(cpu)) & ASID_VERSION_MASK) get_new_mmu_context(next, cpu); @@ -156,6 +156,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, */ cpumask_clear_cpu(cpu, mm_cpumask(prev)); cpumask_set_cpu(cpu, mm_cpumask(next)); + htw_start(); local_irq_restore(flags); } @@ -182,6 +183,7 @@ activate_mm(struct mm_struct *prev, struct mm_struct *next) local_irq_save(flags); + htw_stop(); /* Unconditionally get a new ASID. */ get_new_mmu_context(next, cpu); @@ -191,6 +193,7 @@ activate_mm(struct mm_struct *prev, struct mm_struct *next) /* mark mmu ownership change */ cpumask_clear_cpu(cpu, mm_cpumask(prev)); cpumask_set_cpu(cpu, mm_cpumask(next)); + htw_start(); local_irq_restore(flags); } @@ -205,6 +208,7 @@ drop_mmu_context(struct mm_struct *mm, unsigned cpu) unsigned long flags; local_irq_save(flags); + htw_stop(); if (cpumask_test_cpu(cpu, mm_cpumask(mm))) { get_new_mmu_context(mm, cpu); @@ -213,6 +217,7 @@ drop_mmu_context(struct mm_struct *mm, unsigned cpu) /* will get a new context next time */ cpu_context(cpu, mm) = 0; } + htw_start(); local_irq_restore(flags); } diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h index 3aa982b..845016d 100644 --- a/arch/mips/include/asm/pgtable.h +++ b/arch/mips/include/asm/pgtable.h @@ -99,19 +99,31 @@ extern void paging_init(void); #define htw_stop() \ do { \ + unsigned long flags; \ + \ if (cpu_has_htw) { \ - write_c0_pwctl(read_c0_pwctl() & \ - ~(1 << MIPS_PWCTL_PWEN_SHIFT)); \ - back_to_back_c0_hazard(); \ + local_irq_save(flags); \ + if(!raw_current_cpu_data.htw_seq++) { \ + write_c0_pwctl(read_c0_pwctl() & \ + ~(1 << MIPS_PWCTL_PWEN_SHIFT)); \ + back_to_back_c0_hazard(); \ + } \ + local_irq_restore(flags); \ } \ } while(0) #define htw_start() \ do { \ + unsigned long flags; \ + \ if (cpu_has_htw) { \ - write_c0_pwctl(read_c0_pwctl() | \ - (1 << MIPS_PWCTL_PWEN_SHIFT)); \ - back_to_back_c0_hazard(); \ + local_irq_save(flags); \ + if (!--raw_current_cpu_data.htw_seq) { \ + write_c0_pwctl(read_c0_pwctl() | \ + (1 << MIPS_PWCTL_PWEN_SHIFT)); \ + back_to_back_c0_hazard(); \ + } \ + local_irq_restore(flags); \ } \ } while(0) diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c index 5342674..228ae86 100644 --- a/arch/mips/kernel/cpu-probe.c +++ b/arch/mips/kernel/cpu-probe.c @@ -424,8 +424,10 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c) if (config3 & MIPS_CONF3_MSA) c->ases |= MIPS_ASE_MSA; /* Only tested on 32-bit cores */ - if ((config3 & MIPS_CONF3_PW) && config_enabled(CONFIG_32BIT)) + if ((config3 & MIPS_CONF3_PW) && config_enabled(CONFIG_32BIT)) { + c->htw_seq = 0; c->options |= MIPS_CPU_HTW; + } return config3 & MIPS_CONF_M; } -- 2.7.4