Commit-ID: a66734297f78707ce39d756b656bfae861d53f62 Gitweb: http://git.kernel.org/tip/a66734297f78707ce39d756b656bfae861d53f62 Author: Andy Lutomirski <[email protected]> AuthorDate: Fri, 24 Oct 2014 15:58:13 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 4 Feb 2015 12:10:49 +0100
perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks While perfmon2 is a sufficiently evil library (it pokes MSRs directly) that breaking it is fair game, it's still useful, so we might as well try to support it. This allows users to write 2 to /sys/devices/cpu/rdpmc to disable all rdpmc protection so that hack like perfmon2 can continue to work. At some point, if perf_event becomes fast enough to replace perfmon2, then this can go. Signed-off-by: Andy Lutomirski <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Kees Cook <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Vince Weaver <[email protected]> Cc: "hillf.zj" <[email protected]> Cc: Valdis Kletnieks <[email protected]> Cc: Linus Torvalds <[email protected]> Link: http://lkml.kernel.org/r/caac3c1c707dcca48ecbc35f4def21495856f479.1414190806.git.l...@amacapital.net Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/mmu_context.h | 5 ++++- arch/x86/kernel/cpu/perf_event.c | 21 ++++++++++++++++++++- 2 files changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 89c1fec..883f6b9 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -19,9 +19,12 @@ static inline void paravirt_activate_mm(struct mm_struct *prev, #endif /* !CONFIG_PARAVIRT */ #ifdef CONFIG_PERF_EVENTS +extern struct static_key rdpmc_always_available; + static inline void load_mm_cr4(struct mm_struct *mm) { - if (atomic_read(&mm->context.perf_rdpmc_allowed)) + if (static_key_true(&rdpmc_always_available) || + atomic_read(&mm->context.perf_rdpmc_allowed)) cr4_set_bits(X86_CR4_PCE); else cr4_clear_bits(X86_CR4_PCE); diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index bec5cff..b71a7f8 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -45,6 +45,8 @@ DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = { .enabled = 1, }; +struct static_key rdpmc_always_available = STATIC_KEY_INIT_FALSE; + u64 __read_mostly hw_cache_event_ids [PERF_COUNT_HW_CACHE_MAX] [PERF_COUNT_HW_CACHE_OP_MAX] @@ -1870,10 +1872,27 @@ static ssize_t set_attr_rdpmc(struct device *cdev, if (ret) return ret; + if (val > 2) + return -EINVAL; + if (x86_pmu.attr_rdpmc_broken) return -ENOTSUPP; - x86_pmu.attr_rdpmc = !!val; + if ((val == 2) != (x86_pmu.attr_rdpmc == 2)) { + /* + * Changing into or out of always available, aka + * perf-event-bypassing mode. This path is extremely slow, + * but only root can trigger it, so it's okay. + */ + if (val == 2) + static_key_slow_inc(&rdpmc_always_available); + else + static_key_slow_dec(&rdpmc_always_available); + on_each_cpu(refresh_pce, NULL, 1); + } + + x86_pmu.attr_rdpmc = val; + return count; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
