RE: [PATCH V2 1/1] Drivers: hv: vmbus: Implement a clockevent device

From: KY Srinivasan
Date: Fri Dec 05 2014 - 18:00:31 EST

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In reply to: Jason Wang: "Re: [PATCH V2 1/1] Drivers: hv: vmbus: Implement a clockevent device"
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> -----Original Message-----
> From: Jason Wang [mailto:jasowang@xxxxxxxxxx]
> Sent: Thursday, December 4, 2014 10:52 PM
> To: KY Srinivasan
> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; KY
> Srinivasan
> Subject: Re: [PATCH V2 1/1] Drivers: hv: vmbus: Implement a clockevent
> device
>
>
>
> On Fri, Dec 5, 2014 at 10:18 AM, K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> wrote:
> > Implement a clockevent device based on the timer support available on
> > Hyper-V.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > ---
> > arch/x86/include/uapi/asm/hyperv.h | 11 +++++
> > drivers/hv/hv.c | 78
> > ++++++++++++++++++++++++++++++++++++
> > drivers/hv/hyperv_vmbus.h | 21 ++++++++++
> > drivers/hv/vmbus_drv.c | 40 +++++++++++++++++-
> > 4 files changed, 148 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/include/uapi/asm/hyperv.h
> > b/arch/x86/include/uapi/asm/hyperv.h
> > index 462efe7..90c458e 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 3e4235c..e2749c0
> > 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 c386d8d..44b1c94 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
> > 4d6b269..9e57c07 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 +579,37 @@ 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 (msg->header.message_type == HVMSG_NONE)
> > + return;
>
> Nitpick: caller has checked this.

Yes indeed; I will fix it and resend.
> >
> > +
> > + 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 +699,12 @@ 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);
> > + }
> > }
> >
> > /*
> > --
> > 1.7.4.1
>
> Reviewed-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks Jason.

K. Y

Next message: Greg Kroah-Hartman: "[PATCH 3.14 71/73] batman: fix a bogus warning from batadv_is_on_batman_iface()"
Previous message: Greg Kroah-Hartman: "[PATCH 3.14 68/73] bitops: Fix shift overflow in GENMASK macros"
In reply to: Jason Wang: "Re: [PATCH V2 1/1] Drivers: hv: vmbus: Implement a clockevent device"
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