[Xen-devel] [PATCH v4 3/4] x86: track when in #MC context

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

Add helpers to track when executing in #MC handler context. This is
modeled after the in_irq helpers.

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

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v3:
 - Rename to in_mce_handler.
 - Drop parentheses around cpu in macro.

Changes since v2:
 - Move definition of mc_count to x86 hardirq.h.
---
 xen/arch/x86/cpu/mcheck/mce.c | 2 ++
 xen/include/asm-x86/hardirq.h | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index d61e582af3..e5bd4f542c 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -93,7 +93,9 @@ void x86_mce_vector_register(x86_mce_vector_t hdlr)
 
 void do_machine_check(const struct cpu_user_regs *regs)
 {
+    mce_enter();
     _machine_check_vector(regs);
+    mce_exit();
 }
 
 /*
diff --git a/xen/include/asm-x86/hardirq.h b/xen/include/asm-x86/hardirq.h
index 069e48fce9..276e3419d7 100644
--- a/xen/include/asm-x86/hardirq.h
+++ b/xen/include/asm-x86/hardirq.h
@@ -8,6 +8,7 @@ typedef struct {
        unsigned int __softirq_pending;
        unsigned int __local_irq_count;
        unsigned int nmi_count;
+       unsigned int mce_count;
        bool_t __mwait_wakeup;
 } __cacheline_aligned irq_cpustat_t;
 
@@ -23,6 +24,11 @@ typedef struct {
 #define nmi_enter()            (nmi_count(smp_processor_id())++)
 #define nmi_exit()             (nmi_count(smp_processor_id())--)
 
+#define mce_count(cpu)         __IRQ_STAT(cpu, mce_count)
+#define in_mce_handler()       (mce_count(smp_processor_id()) != 0)
+#define mce_enter()            (mce_count(smp_processor_id())++)
+#define mce_exit()             (mce_count(smp_processor_id())--)
+
 void ack_bad_irq(unsigned int irq);
 
 extern void apic_intr_init(void);
-- 
2.25.0


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