From: Don Zickus Date: Thu, 6 Jan 2011 21:18:51 +0000 (-0500) Subject: x86, NMI: Allow NMI reason io port (0x61) to be processed on any CPU X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ab846f13f69fa64f8ed69ce0c3e239e075910d23;p=linux-beck.git x86, NMI: Allow NMI reason io port (0x61) to be processed on any CPU In original NMI handler, NMI reason io port (0x61) is only processed on BSP. This makes it impossible to hot-remove BSP. To solve the issue, a raw spinlock is used to allow the port to be processed on any CPU. Originally-by: Huang Ying Signed-off-by: Don Zickus Signed-off-by: Peter Zijlstra LKML-Reference: <1294348732-15030-6-git-send-email-dzickus@redhat.com> Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 23f6ac05d04c..613b3d284a89 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -84,6 +84,11 @@ EXPORT_SYMBOL_GPL(used_vectors); static int ignore_nmis; int unknown_nmi_panic; +/* + * Prevent NMI reason port (0x61) being accessed simultaneously, can + * only be used in NMI handler. + */ +static DEFINE_RAW_SPINLOCK(nmi_reason_lock); static inline void conditional_sti(struct pt_regs *regs) { @@ -392,7 +397,6 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs) static notrace __kprobes void default_do_nmi(struct pt_regs *regs) { unsigned char reason = 0; - int cpu; /* * CPU-specific NMI must be processed before non-CPU-specific @@ -402,13 +406,12 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs) if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP) return; - cpu = smp_processor_id(); - - /* Only the BSP gets external NMIs from the system. */ - if (!cpu) - reason = get_nmi_reason(); + /* Non-CPU-specific NMI: NMI sources can be processed on any CPU */ + raw_spin_lock(&nmi_reason_lock); + reason = get_nmi_reason(); if (!(reason & NMI_REASON_MASK)) { + raw_spin_unlock(&nmi_reason_lock); unknown_nmi_error(reason, regs); return; @@ -426,6 +429,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs) */ reassert_nmi(); #endif + raw_spin_unlock(&nmi_reason_lock); } dotraplinkage notrace __kprobes void