10 files changed, 131 insertions, 5 deletions

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 6ad064c8cf35..bef8e2b202a8 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 805f52703ee3..5a11e324eacc 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 7c341a74ec8c..5ea2afd4c871 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 e71c1120426b..404c5fdff859 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 25283f7eb299..e73c4d0c06ad 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 099414345865..6c0c3a3b631c 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 9340f41ce8d3..4488cf0dd499 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 45fb4d2565f8..328d027d829d 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)
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 31142b72f1b9..b1f6793acf4c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -27,7 +27,7 @@
 #include <linux/vmalloc.h>
 #include <linux/hyperv.h>
 #include <linux/version.h>
-#include <linux/interrupt.h>
+#include <linux/random.h>
 #include <linux/clockchips.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>
@@ -38,6 +38,17 @@ struct hv_context hv_context = {
         .synic_initialized      = false,
 };
 
+/*
+ * If false, we're using the old mechanism for stimer0 interrupts
+ * where it sends a VMbus message when it expires. The old
+ * mechanism is used when running on older versions of Hyper-V
+ * that don't support Direct Mode. While Hyper-V provides
+ * four stimer's per CPU, Linux uses only stimer0.
+ */
+static bool direct_mode_enabled;
+static int stimer0_irq;
+static int stimer0_vector;
+
 #define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
 #define HV_MAX_MAX_DELTA_TICKS 0xffffffff
 #define HV_MIN_DELTA_TICKS 1
@@ -53,6 +64,8 @@ int hv_init(void)
         if (!hv_context.cpu_context)
                 return -ENOMEM;
 
+        direct_mode_enabled = ms_hyperv.misc_features &
+                        HV_X64_STIMER_DIRECT_MODE_AVAILABLE;
         return 0;
 }
 
@@ -91,6 +104,21 @@ int hv_post_message(union hv_connection_id connection_id,
         return status & 0xFFFF;
 }
 
+/*
+ * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
+ * does not use VMbus or any VMbus messages, so process here and not
+ * in the VMbus driver code.
+ */
+
+static void hv_stimer0_isr(void)
+{
+        struct hv_per_cpu_context *hv_cpu;
+
+        hv_cpu = this_cpu_ptr(hv_context.cpu_context);
+        hv_cpu->clk_evt->event_handler(hv_cpu->clk_evt);
+        add_interrupt_randomness(stimer0_vector, 0);
+}
+
 static int hv_ce_set_next_event(unsigned long delta,
                                 struct clock_event_device *evt)
 {
@@ -108,6 +136,8 @@ static int hv_ce_shutdown(struct clock_event_device *evt)
 {
         hv_init_timer(HV_X64_MSR_STIMER0_COUNT, 0);
         hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, 0);
+        if (direct_mode_enabled)
+                hv_disable_stimer0_percpu_irq(stimer0_irq);
 
         return 0;
 }
@@ -116,11 +146,26 @@ static int hv_ce_set_oneshot(struct clock_event_device *evt)
 {
         union hv_timer_config timer_cfg;
 
+        timer_cfg.as_uint64 = 0;
         timer_cfg.enable = 1;
         timer_cfg.auto_enable = 1;
-        timer_cfg.sintx = VMBUS_MESSAGE_SINT;
+        if (direct_mode_enabled) {
+                /*
+                 * When it expires, the timer will directly interrupt
+                 * on the specified hardware vector/IRQ.
+                 */
+                timer_cfg.direct_mode = 1;
+                timer_cfg.apic_vector = stimer0_vector;
+                hv_enable_stimer0_percpu_irq(stimer0_irq);
+        } else {
+                /*
+                 * When it expires, the timer will generate a VMbus message,
+                 * to be handled by the normal VMbus interrupt handler.
+                 */
+                timer_cfg.direct_mode = 0;
+                timer_cfg.sintx = VMBUS_MESSAGE_SINT;
+        }
         hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, timer_cfg.as_uint64);
-
         return 0;
 }
 
@@ -191,6 +236,11 @@ int hv_synic_alloc(void)
                 INIT_LIST_HEAD(&hv_cpu->chan_list);
         }
 
+        if (direct_mode_enabled &&
+            hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
+                                hv_stimer0_isr))
+                goto err;
+
         return 0;
 err:
         return -ENOMEM;
@@ -292,6 +342,9 @@ void hv_synic_clockevents_cleanup(void)
         if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
                 return;
 
+        if (direct_mode_enabled)
+                hv_remove_stimer0_irq(stimer0_irq);
+
         for_each_present_cpu(cpu) {
                 struct hv_per_cpu_context *hv_cpu
                         = per_cpu_ptr(hv_context.cpu_context, cpu);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 22300ec7b556..36d34fe3ccb3 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -57,7 +57,9 @@ union hv_timer_config {
                 u64 periodic:1;
                 u64 lazy:1;
                 u64 auto_enable:1;
-                u64 reserved_z0:12;
+                u64 apic_vector:8;
+                u64 direct_mode:1;
+                u64 reserved_z0:3;
                 u64 sintx:4;
                 u64 reserved_z1:44;
         };