[PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as special hypervisor interrupts

["K. Y. Srinivasan" <kys@microsoft.com>]

Starting with win8, vmbus interrupts can be delivered on any VCPU in the guest and
furthermore can be concurrently active on multiple VCPUs. Support this interrupt
delivery model by setting up a separate IDT entry for Hyper-V vmbus interrupts.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 arch/x86/include/asm/irq_vectors.h |    2 +
 arch/x86/include/asm/mshyperv.h    |    4 +++
 arch/x86/kernel/cpu/mshyperv.c     |   39 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/entry_32.S         |    7 ++++++
 arch/x86/kernel/entry_64.S         |    5 ++++
 5 files changed, 57 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 1508e51..c2ff239 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -112,6 +112,8 @@
 /* Xen vector callback to receive events in a HVM domain */
 #define XEN_HVM_EVTCHN_CALLBACK		0xf3
 
+/* Hyper-V vector callback to receive vmbus interrupts*/
+#define HYPER_V_CALLBACK_VECTOR		0xf2
 /*
  * Local APIC timer IRQ vector is on a different priority level,
  * to work around the 'lost local interrupt if more than 2 IRQ
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 79ce568..c2934be 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -11,4 +11,8 @@ struct ms_hyperv_info {
 
 extern struct ms_hyperv_info ms_hyperv;
 
+void hyperv_callback_vector(void);
+void hyperv_vector_handler(struct pt_regs *regs);
+void hv_register_vmbus_handler(int irq, irq_handler_t handler);
+
 #endif
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 0a630dd..03be583 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -14,10 +14,15 @@
 #include <linux/time.h>
 #include <linux/clocksource.h>
 #include <linux/module.h>
+#include <linux/hardirq.h>
+#include <linux/interrupt.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>
+#include <asm/desc.h>
+#include <asm/idle.h>
+#include <asm/irq_regs.h>
 
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -69,6 +74,11 @@ static void __init ms_hyperv_init_platform(void)
 	       ms_hyperv.features, ms_hyperv.hints);
 
 	clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
+
+	/*
+	 * Setup the IDT for hypervisor callback.
+	 */
+	alloc_intr_gate(HYPER_V_CALLBACK_VECTOR, hyperv_callback_vector);
 }
 
 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
@@ -77,3 +87,32 @@ const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
 	.init_platform		= ms_hyperv_init_platform,
 };
 EXPORT_SYMBOL(x86_hyper_ms_hyperv);
+
+static int vmbus_irq;
+static irq_handler_t vmbus_isr;
+
+void hv_register_vmbus_handler(int irq, irq_handler_t handler)
+{
+	vmbus_irq = irq;
+	vmbus_isr = handler;
+}
+EXPORT_SYMBOL_GPL(hv_register_vmbus_handler);
+
+void hyperv_vector_handler(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+	struct irq_desc *desc;
+
+	irq_enter();
+#ifdef CONFIG_X86
+	exit_idle();
+#endif
+
+	desc = irq_to_desc(vmbus_irq);
+
+	if (desc)
+		generic_handle_irq_desc(vmbus_irq, desc);
+
+	irq_exit();
+	set_irq_regs(old_regs);
+}
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index e9dd4c4..7743876 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1052,6 +1052,13 @@ BUILD_INTERRUPT3(xen_hvm_callback_vector, XEN_HVM_EVTCHN_CALLBACK,
 
 #endif	/* CONFIG_XEN */
 
+#if IS_ENABLED(CONFIG_HYPERV)
+
+BUILD_INTERRUPT3(hyperv_callback_vector, HYPER_V_CALLBACK_VECTOR,
+	hyperv_vector_handler)
+
+#endif /* CONFIG_HYPERV */
+
 #ifdef CONFIG_FUNCTION_TRACER
 #ifdef CONFIG_DYNAMIC_FTRACE
 
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1975122..a1cb724 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1451,6 +1451,11 @@ apicinterrupt XEN_HVM_EVTCHN_CALLBACK \
 
 #endif /* CONFIG_XEN */
 
+#if IS_ENABLED(CONFIG_HYPERV)
+apicinterrupt HYPER_V_CALLBACK_VECTOR \
+	hyperv_callback_vector hyperv_vector_handler
+#endif /* CONFIG_HYPERV */
+
 /*
  * Some functions should be protected against kprobes
  */
-- 
1.7.4.1