From: Peter Zijlstra <[email protected]> Since there are already a number of sites (ARM64, PowerPC) that effectively nest nmi_enter(), make the primitive support this before adding even more.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Marc Zyngier <[email protected]> Acked-by: Will Deacon <[email protected]> Cc: Michael Ellerman <[email protected]> --- arch/arm64/kernel/sdei.c | 14 ++------------ arch/arm64/kernel/traps.c | 8 ++------ arch/powerpc/kernel/traps.c | 22 ++++++---------------- include/linux/hardirq.h | 5 ++++- include/linux/preempt.h | 4 ++-- 5 files changed, 16 insertions(+), 37 deletions(-) --- a/arch/arm64/kernel/sdei.c +++ b/arch/arm64/kernel/sdei.c @@ -251,22 +251,12 @@ asmlinkage __kprobes notrace unsigned lo __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) { unsigned long ret; - bool do_nmi_exit = false; - /* - * nmi_enter() deals with printk() re-entrance and use of RCU when - * RCU believed this CPU was idle. Because critical events can - * interrupt normal events, we may already be in_nmi(). - */ - if (!in_nmi()) { - nmi_enter(); - do_nmi_exit = true; - } + nmi_enter(); ret = _sdei_handler(regs, arg); - if (do_nmi_exit) - nmi_exit(); + nmi_exit(); return ret; } --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -906,17 +906,13 @@ bool arm64_is_fatal_ras_serror(struct pt asmlinkage void do_serror(struct pt_regs *regs, unsigned int esr) { - const bool was_in_nmi = in_nmi(); - - if (!was_in_nmi) - nmi_enter(); + nmi_enter(); /* non-RAS errors are not containable */ if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(regs, esr)) arm64_serror_panic(regs, esr); - if (!was_in_nmi) - nmi_exit(); + nmi_exit(); } asmlinkage void enter_from_user_mode(void) --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -441,15 +441,9 @@ void hv_nmi_check_nonrecoverable(struct void system_reset_exception(struct pt_regs *regs) { unsigned long hsrr0, hsrr1; - bool nested = in_nmi(); bool saved_hsrrs = false; - /* - * Avoid crashes in case of nested NMI exceptions. Recoverability - * is determined by RI and in_nmi - */ - if (!nested) - nmi_enter(); + nmi_enter(); /* * System reset can interrupt code where HSRRs are live and MSR[RI]=1. @@ -521,8 +515,7 @@ void system_reset_exception(struct pt_re mtspr(SPRN_HSRR1, hsrr1); } - if (!nested) - nmi_exit(); + nmi_exit(); /* What should we do here? We could issue a shutdown or hard reset. */ } @@ -823,9 +816,8 @@ int machine_check_generic(struct pt_regs void machine_check_exception(struct pt_regs *regs) { int recover = 0; - bool nested = in_nmi(); - if (!nested) - nmi_enter(); + + nmi_enter(); __this_cpu_inc(irq_stat.mce_exceptions); @@ -851,8 +843,7 @@ void machine_check_exception(struct pt_r if (check_io_access(regs)) goto bail; - if (!nested) - nmi_exit(); + nmi_exit(); die("Machine check", regs, SIGBUS); @@ -863,8 +854,7 @@ void machine_check_exception(struct pt_r return; bail: - if (!nested) - nmi_exit(); + nmi_exit(); } void SMIException(struct pt_regs *regs) --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -65,13 +65,16 @@ extern void irq_exit(void); #define arch_nmi_exit() do { } while (0) #endif +/* + * nmi_enter() can nest up to 15 times; see NMI_BITS. + */ #define nmi_enter() \ do { \ arch_nmi_enter(); \ printk_nmi_enter(); \ lockdep_off(); \ ftrace_nmi_enter(); \ - BUG_ON(in_nmi()); \ + BUG_ON(in_nmi() == NMI_MASK); \ preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \ rcu_nmi_enter(); \ lockdep_hardirq_enter(); \ --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -26,13 +26,13 @@ * PREEMPT_MASK: 0x000000ff * SOFTIRQ_MASK: 0x0000ff00 * HARDIRQ_MASK: 0x000f0000 - * NMI_MASK: 0x00100000 + * NMI_MASK: 0x00f00000 * PREEMPT_NEED_RESCHED: 0x80000000 */ #define PREEMPT_BITS 8 #define SOFTIRQ_BITS 8 #define HARDIRQ_BITS 4 -#define NMI_BITS 1 +#define NMI_BITS 4 #define PREEMPT_SHIFT 0 #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS)
