Drivers: hv: vmbus: Implement a clockevent device

Implement a clockevent device based on the timer support available on
Hyper-V.
In this version of the patch I have addressed Jason's review comments.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 145 insertions, 2 deletions

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 462efe746d77..90c458e66e13 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -187,6 +187,17 @@
 #define HV_X64_MSR_SINT14                       0x4000009E
 #define HV_X64_MSR_SINT15                       0x4000009F
 
+/*
+ * Synthetic Timer MSRs. Four timers per vcpu.
+ */
+#define HV_X64_MSR_STIMER0_CONFIG               0x400000B0
+#define HV_X64_MSR_STIMER0_COUNT                0x400000B1
+#define HV_X64_MSR_STIMER1_CONFIG               0x400000B2
+#define HV_X64_MSR_STIMER1_COUNT                0x400000B3
+#define HV_X64_MSR_STIMER2_CONFIG               0x400000B4
+#define HV_X64_MSR_STIMER2_COUNT                0x400000B5
+#define HV_X64_MSR_STIMER3_CONFIG               0x400000B6
+#define HV_X64_MSR_STIMER3_COUNT                0x400000B7
 
 #define HV_X64_MSR_HYPERCALL_ENABLE             0x00000001
 #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT 12
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 3e4235c7a47f..50e51a51ff8b 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -28,7 +28,9 @@
 #include <linux/hyperv.h>
 #include <linux/version.h>
 #include <linux/interrupt.h>
+#include <linux/clockchips.h>
 #include <asm/hyperv.h>
+#include <asm/mshyperv.h>
 #include "hyperv_vmbus.h"
 
 /* The one and only */
@@ -37,6 +39,10 @@ struct hv_context hv_context = {
         .hypercall_page         = NULL,
 };
 
+#define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
+#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
+#define HV_MIN_DELTA_TICKS 1
+
 /*
  * query_hypervisor_info - Get version info of the windows hypervisor
  */
@@ -144,6 +150,8 @@ int hv_init(void)
                sizeof(int) * NR_CPUS);
         memset(hv_context.event_dpc, 0,
                sizeof(void *) * NR_CPUS);
+        memset(hv_context.clk_evt, 0,
+               sizeof(void *) * NR_CPUS);
 
         max_leaf = query_hypervisor_info();
 
@@ -258,10 +266,63 @@ u16 hv_signal_event(void *con_id)
         return status;
 }
 
+static int hv_ce_set_next_event(unsigned long delta,
+                                struct clock_event_device *evt)
+{
+        cycle_t current_tick;
+
+        WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
+
+        rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+        current_tick += delta;
+        wrmsrl(HV_X64_MSR_STIMER0_COUNT, current_tick);
+        return 0;
+}
+
+static void hv_ce_setmode(enum clock_event_mode mode,
+                          struct clock_event_device *evt)
+{
+        union hv_timer_config timer_cfg;
+
+        switch (mode) {
+        case CLOCK_EVT_MODE_PERIODIC:
+                /* unsupported */
+                break;
+
+        case CLOCK_EVT_MODE_ONESHOT:
+                timer_cfg.enable = 1;
+                timer_cfg.auto_enable = 1;
+                timer_cfg.sintx = VMBUS_MESSAGE_SINT;
+                wrmsrl(HV_X64_MSR_STIMER0_CONFIG, timer_cfg.as_uint64);
+                break;
+
+        case CLOCK_EVT_MODE_UNUSED:
+        case CLOCK_EVT_MODE_SHUTDOWN:
+                wrmsrl(HV_X64_MSR_STIMER0_COUNT, 0);
+                wrmsrl(HV_X64_MSR_STIMER0_CONFIG, 0);
+                break;
+        case CLOCK_EVT_MODE_RESUME:
+                break;
+        }
+}
+
+static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
+{
+        dev->name = "Hyper-V clockevent";
+        dev->features = CLOCK_EVT_FEAT_ONESHOT;
+        dev->cpumask = cpumask_of(cpu);
+        dev->rating = 1000;
+        dev->owner = THIS_MODULE;
+
+        dev->set_mode = hv_ce_setmode;
+        dev->set_next_event = hv_ce_set_next_event;
+}
+
 
 int hv_synic_alloc(void)
 {
         size_t size = sizeof(struct tasklet_struct);
+        size_t ced_size = sizeof(struct clock_event_device);
         int cpu;
 
         for_each_online_cpu(cpu) {
@@ -272,6 +333,13 @@ int hv_synic_alloc(void)
                 }
                 tasklet_init(hv_context.event_dpc[cpu], vmbus_on_event, cpu);
 
+                hv_context.clk_evt[cpu] = kzalloc(ced_size, GFP_ATOMIC);
+                if (hv_context.clk_evt[cpu] == NULL) {
+                        pr_err("Unable to allocate clock event device\n");
+                        goto err;
+                }
+                hv_init_clockevent_device(hv_context.clk_evt[cpu], cpu);
+
                 hv_context.synic_message_page[cpu] =
                         (void *)get_zeroed_page(GFP_ATOMIC);
 
@@ -305,6 +373,7 @@ err:
 static void hv_synic_free_cpu(int cpu)
 {
         kfree(hv_context.event_dpc[cpu]);
+        kfree(hv_context.clk_evt[cpu]);
         if (hv_context.synic_event_page[cpu])
                 free_page((unsigned long)hv_context.synic_event_page[cpu]);
         if (hv_context.synic_message_page[cpu])
@@ -388,6 +457,15 @@ void hv_synic_init(void *arg)
         hv_context.vp_index[cpu] = (u32)vp_index;
 
         INIT_LIST_HEAD(&hv_context.percpu_list[cpu]);
+
+        /*
+         * Register the per-cpu clockevent source.
+         */
+        if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
+                clockevents_config_and_register(hv_context.clk_evt[cpu],
+                                                HV_TIMER_FREQUENCY,
+                                                HV_MIN_DELTA_TICKS,
+                                                HV_MAX_MAX_DELTA_TICKS);
         return;
 }
 
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index c386d8dc7223..44b1c9424712 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -178,6 +178,23 @@ struct hv_message_header {
         };
 };
 
+/*
+ * Timer configuration register.
+ */
+union hv_timer_config {
+        u64 as_uint64;
+        struct {
+                u64 enable:1;
+                u64 periodic:1;
+                u64 lazy:1;
+                u64 auto_enable:1;
+                u64 reserved_z0:12;
+                u64 sintx:4;
+                u64 reserved_z1:44;
+        };
+};
+
+
 /* Define timer message payload structure. */
 struct hv_timer_message_payload {
         u32 timer_index;
@@ -519,6 +536,10 @@ struct hv_context {
          * buffer to post messages to the host.
          */
         void *post_msg_page[NR_CPUS];
+        /*
+         * Support PV clockevent device.
+         */
+        struct clock_event_device *clk_evt[NR_CPUS];
 };
 
 extern struct hv_context hv_context;
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4d6b26979fbd..7488111ec057 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -32,6 +32,7 @@
 #include <linux/completion.h>
 #include <linux/hyperv.h>
 #include <linux/kernel_stat.h>
+#include <linux/clockchips.h>
 #include <asm/hyperv.h>
 #include <asm/hypervisor.h>
 #include <asm/mshyperv.h>
@@ -578,6 +579,34 @@ static void vmbus_onmessage_work(struct work_struct *work)
         kfree(ctx);
 }
 
+void hv_process_timer_expiration(struct hv_message *msg, int cpu)
+{
+        struct clock_event_device *dev = hv_context.clk_evt[cpu];
+
+        if (dev->event_handler)
+                dev->event_handler(dev);
+
+        msg->header.message_type = HVMSG_NONE;
+
+        /*
+         * Make sure the write to MessageType (ie set to
+         * HVMSG_NONE) happens before we read the
+         * MessagePending and EOMing. Otherwise, the EOMing
+         * will not deliver any more messages since there is
+         * no empty slot
+         */
+        mb();
+
+        if (msg->header.message_flags.msg_pending) {
+                /*
+                 * This will cause message queue rescan to
+                 * possibly deliver another msg from the
+                 * hypervisor
+                 */
+                wrmsrl(HV_X64_MSR_EOM, 0);
+        }
+}
+
 static void vmbus_on_msg_dpc(unsigned long data)
 {
         int cpu = smp_processor_id();
@@ -667,8 +696,12 @@ static void vmbus_isr(void)
         msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
 
         /* Check if there are actual msgs to be processed */
-        if (msg->header.message_type != HVMSG_NONE)
-                tasklet_schedule(&msg_dpc);
+        if (msg->header.message_type != HVMSG_NONE) {
+                if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
+                        hv_process_timer_expiration(msg, cpu);
+                else
+                        tasklet_schedule(&msg_dpc);
+        }
 }
 
 /*