[Xen-devel] [PATCH v2 4/6] x86: track when in #NMI context

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Add helpers to track when running in #MC context. This is modeled
after the in_irq helpers, but does not support reentry.

Note that there are no users of in_mc() introduced by the change,
further users will be added by followup changes.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/traps.c          |  6 ++++++
 xen/include/asm-x86/hardirq.h | 18 +++++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 3dbc66bb64..f4f2c13ae9 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1692,9 +1692,13 @@ void do_nmi(const struct cpu_user_regs *regs)
     bool handle_unknown = false;
 
     this_cpu(nmi_count)++;
+    nmi_enter();
 
     if ( nmi_callback(regs, cpu) )
+    {
+        nmi_exit();
         return;
+    }
 
     /*
      * Accessing port 0x61 may trap to SMM which has been actually
@@ -1720,6 +1724,8 @@ void do_nmi(const struct cpu_user_regs *regs)
         if ( !(reason & 0xc0) && handle_unknown )
             unknown_nmi_error(regs, reason);
     }
+
+    nmi_exit();
 }
 
 nmi_callback_t *set_nmi_callback(nmi_callback_t *callback)
diff --git a/xen/include/asm-x86/hardirq.h b/xen/include/asm-x86/hardirq.h
index af3eab6a4d..8bcae99eac 100644
--- a/xen/include/asm-x86/hardirq.h
+++ b/xen/include/asm-x86/hardirq.h
@@ -2,12 +2,14 @@
 #define __ASM_HARDIRQ_H
 
 #include <xen/cache.h>
+#include <xen/lib.h>
+#include <xen/smp.h>
 #include <xen/types.h>
 
 typedef struct {
        unsigned int __softirq_pending;
        unsigned int __local_irq_count;
-       unsigned int __nmi_count;
+       bool in_nmi;
        unsigned int mc_count;
        bool_t __mwait_wakeup;
 } __cacheline_aligned irq_cpustat_t;
@@ -23,6 +25,20 @@ typedef struct {
 #define mc_enter()     (mc_count(smp_processor_id())++)
 #define mc_exit()      (mc_count(smp_processor_id())--)
 
+#define in_nmi()       __IRQ_STAT(smp_processor_id(), in_nmi)
+
+static inline void nmi_enter(void)
+{
+    ASSERT(!in_nmi());
+    in_nmi() = true;
+}
+
+static inline void nmi_exit(void)
+{
+    ASSERT(in_nmi());
+    in_nmi() = false;
+}
+
 void ack_bad_irq(unsigned int irq);
 
 extern void apic_intr_init(void);
-- 
2.25.0


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