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Subject[PATCH 5/6] x86, NMI: Allow NMI reason io port (0x61) to be processed on any CPU
Date
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 make the port can be processed on any
CPU.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>

Conflicts:

arch/x86/kernel/traps.c
---
arch/x86/kernel/traps.c | 36 +++++++++++++++++++-----------------
1 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 79b9b2f..ed40ad6 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -83,6 +83,12 @@ EXPORT_SYMBOL_GPL(used_vectors);

static int ignore_nmis;

+/*
+ * 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)
{
if (regs->flags & X86_EFLAGS_IF)
@@ -383,7 +389,6 @@ 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
@@ -399,25 +404,22 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
return;

/* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
- cpu = smp_processor_id();
- /* Only the BSP gets external NMIs from the system. */
- if (!cpu) {
- reason = get_nmi_reason();
- if (reason & NMI_REASON_MASK) {
- if (reason & NMI_REASON_SERR)
- pci_serr_error(reason, regs);
- else if (reason & NMI_REASON_IOCHK)
- io_check_error(reason, regs);
+ raw_spin_lock(&nmi_reason_lock);
+ reason = get_nmi_reason();
+ if (reason & NMI_REASON_MASK) {
+ if (reason & NMI_REASON_SERR)
+ pci_serr_error(reason, regs);
+ else if (reason & NMI_REASON_IOCHK)
+ io_check_error(reason, regs);
#ifdef CONFIG_X86_32
- /*
- * Reassert NMI in case it became active
- * meanwhile as it's edge-triggered:
- */
- reassert_nmi();
+ /*
+ * Reassert NMI in case it became active
+ * meanwhile as it's edge-triggered:
+ */
+ reassert_nmi();
#endif
- return;
- }
}
+ raw_spin_unlock(&nmi_reason_lock);

#if defined(CONFIG_X86_LOCAL_APIC) && !defined(CONFIG_LOCKUP_DETECTOR)
if (nmi_watchdog_tick(regs, reason))
--
1.7.2.3


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