8 files changed, 72 insertions, 1 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 6ad064c..bef8e2b 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -902,6 +902,9 @@ BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
 BUILD_INTERRUPT3(hyperv_reenlightenment_vector, HYPERV_REENLIGHTENMENT_VECTOR,
 		 hyperv_reenlightenment_intr)
 
+BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR,
+		 hv_stimer0_vector_handler)
+
 #endif /* CONFIG_HYPERV */
 
 ENTRY(page_fault)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 805f527..5a11e32 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1135,6 +1135,9 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
 
 apicinterrupt3 HYPERV_REENLIGHTENMENT_VECTOR \
 	hyperv_reenlightenment_vector hyperv_reenlightenment_intr
+
+apicinterrupt3 HYPERV_STIMER0_VECTOR \
+	hv_stimer0_callback_vector hv_stimer0_vector_handler
 #endif /* CONFIG_HYPERV */
 
 idtentry debug			do_debug		has_error_code=0	paranoid=1 shift_ist=DEBUG_STACK
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 7c341a7..5ea2afd 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -40,6 +40,7 @@ typedef struct {
 #endif
 #if IS_ENABLED(CONFIG_HYPERV)
 	unsigned int irq_hv_reenlightenment_count;
+	unsigned int hyperv_stimer0_count;
 #endif
 } ____cacheline_aligned irq_cpustat_t;
 
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index e71c112..404c5fd 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -106,9 +106,10 @@
 
 #if IS_ENABLED(CONFIG_HYPERV)
 #define HYPERV_REENLIGHTENMENT_VECTOR	0xee
+#define HYPERV_STIMER0_VECTOR		0xed
 #endif
 
-#define LOCAL_TIMER_VECTOR		0xed
+#define LOCAL_TIMER_VECTOR		0xec
 
 #define NR_VECTORS			 256
 
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 25283f7..e73c4d0 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -173,6 +173,19 @@ void hv_remove_kexec_handler(void);
 void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
 void hv_remove_crash_handler(void);
 
+/*
+ * Routines for stimer0 Direct Mode handling.
+ * On x86/x64, there are no percpu actions to take.
+ */
+void hv_stimer0_vector_handler(struct pt_regs *regs);
+void hv_stimer0_callback_vector(void);
+int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void));
+void hv_remove_stimer0_irq(int irq);
+
+static inline void hv_enable_stimer0_percpu_irq(int irq) {}
+static inline void hv_disable_stimer0_percpu_irq(int irq) {}
+
+
 #if IS_ENABLED(CONFIG_HYPERV)
 extern struct clocksource *hyperv_cs;
 extern void *hv_hypercall_pg;
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 0994143..6c0c3a3 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -77,6 +77,9 @@
 /* Crash MSR available */
 #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE (1 << 10)
 
+/* stimer Direct Mode is available */
+#define HV_X64_STIMER_DIRECT_MODE_AVAILABLE	(1 << 19)
+
 /*
  * Feature identification: EBX indicates which flags were specified at
  * partition creation. The format is the same as the partition creation
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 9340f41..4488cf0 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -37,6 +37,7 @@ EXPORT_SYMBOL_GPL(ms_hyperv);
 
 #if IS_ENABLED(CONFIG_HYPERV)
 static void (*vmbus_handler)(void);
+static void (*hv_stimer0_handler)(void);
 static void (*hv_kexec_handler)(void);
 static void (*hv_crash_handler)(struct pt_regs *regs);
 
@@ -69,6 +70,41 @@ void hv_remove_vmbus_irq(void)
 EXPORT_SYMBOL_GPL(hv_setup_vmbus_irq);
 EXPORT_SYMBOL_GPL(hv_remove_vmbus_irq);
 
+/*
+ * Routines to do per-architecture handling of stimer0
+ * interrupts when in Direct Mode
+ */
+
+__visible void __irq_entry hv_stimer0_vector_handler(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
+	entering_irq();
+	inc_irq_stat(hyperv_stimer0_count);
+	if (hv_stimer0_handler)
+		hv_stimer0_handler();
+	ack_APIC_irq();
+
+	exiting_irq();
+	set_irq_regs(old_regs);
+}
+
+int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void))
+{
+	*vector = HYPERV_STIMER0_VECTOR;
+	*irq = 0;   /* Unused on x86/x64 */
+	hv_stimer0_handler = handler;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_setup_stimer0_irq);
+
+void hv_remove_stimer0_irq(int irq)
+{
+	/* We have no way to deallocate the interrupt gate */
+	hv_stimer0_handler = NULL;
+}
+EXPORT_SYMBOL_GPL(hv_remove_stimer0_irq);
+
 void hv_setup_kexec_handler(void (*handler)(void))
 {
 	hv_kexec_handler = handler;
@@ -257,6 +293,10 @@ static void __init ms_hyperv_init_platform(void)
 		alloc_intr_gate(HYPERV_REENLIGHTENMENT_VECTOR,
 				hyperv_reenlightenment_vector);
 
+	/* Setup the IDT for stimer0 */
+	if (ms_hyperv.misc_features & HV_X64_STIMER_DIRECT_MODE_AVAILABLE)
+		alloc_intr_gate(HYPERV_STIMER0_VECTOR,
+				hv_stimer0_callback_vector);
 #endif
 }
 
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 45fb4d2..328d027 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -150,6 +150,13 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 				   irq_stats(j)->irq_hv_reenlightenment_count);
 		seq_puts(p, "  Hyper-V reenlightenment interrupts\n");
 	}
+	if (test_bit(HYPERV_STIMER0_VECTOR, system_vectors)) {
+		seq_printf(p, "%*s: ", prec, "HVS");
+		for_each_online_cpu(j)
+			seq_printf(p, "%10u ",
+				   irq_stats(j)->hyperv_stimer0_count);
+		seq_puts(p, "  Hyper-V stimer0 interrupts\n");
+	}
 #endif
 	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
 #if defined(CONFIG_X86_IO_APIC)