x86: KVM guest: Use the paravirt clocksource structs and functions

This patch updates the kvm host code to use the pvclock structs
and functions, thereby making it compatible with Xen.

The patch also fixes an initialization bug: on SMP systems the
per-cpu has two different locations early at boot and after CPU
bringup.  kvmclock must take that in account when registering the
physical address within the host.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f94bca6ff47f33df81763cc2e9b6841c5a126e63..e0edaaa6920af63832979a04d4f525acafe64e8a 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -383,6 +383,7 @@ config VMI
 config KVM_CLOCK
        bool "KVM paravirtualized clock"
        select PARAVIRT
+       select PARAVIRT_CLOCK
        depends on !(X86_VISWS || X86_VOYAGER)
        help
          Turning on this option will allow you to run a paravirtualized clock

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 08a30986d4725f25ebc316b196884dd8f5aac9d7..87edf1ceb1df32c3afd62d1de44801c286922f7e 100644 (file)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -18,6 +18,7 @@
 
 #include <linux/clocksource.h>
 #include <linux/kvm_para.h>
+#include <asm/pvclock.h>
 #include <asm/arch_hooks.h>
 #include <asm/msr.h>
 #include <asm/apic.h>
@@ -36,18 +37,9 @@ static int parse_no_kvmclock(char *arg)
 early_param("no-kvmclock", parse_no_kvmclock);
 
 /* The hypervisor will put information about time periodically here */
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct kvm_vcpu_time_info, hv_clock);
-#define get_clock(cpu, field) per_cpu(hv_clock, cpu).field
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
+static struct pvclock_wall_clock wall_clock;
 
-static inline u64 kvm_get_delta(u64 last_tsc)
-{
-       int cpu = smp_processor_id();
-       u64 delta = native_read_tsc() - last_tsc;
-       return (delta * get_clock(cpu, tsc_to_system_mul)) >> KVM_SCALE;
-}
-
-static struct kvm_wall_clock wall_clock;
-static cycle_t kvm_clock_read(void);
 /*
  * The wallclock is the time of day when we booted. Since then, some time may
  * have elapsed since the hypervisor wrote the data. So we try to account for
@@ -55,64 +47,37 @@ static cycle_t kvm_clock_read(void);
  */
 static unsigned long kvm_get_wallclock(void)
 {
-       u32 wc_sec, wc_nsec;
-       u64 delta;
+       struct pvclock_vcpu_time_info *vcpu_time;
        struct timespec ts;
-       int version, nsec;
        int low, high;
 
        low = (int)__pa(&wall_clock);
        high = ((u64)__pa(&wall_clock) >> 32);
+       native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
 
-       delta = kvm_clock_read();
+       vcpu_time = &get_cpu_var(hv_clock);
+       pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
+       put_cpu_var(hv_clock);
 
-       native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
-       do {
-               version = wall_clock.wc_version;
-               rmb();
-               wc_sec = wall_clock.wc_sec;
-               wc_nsec = wall_clock.wc_nsec;
-               rmb();
-       } while ((wall_clock.wc_version != version) || (version & 1));
-
-       delta = kvm_clock_read() - delta;
-       delta += wc_nsec;
-       nsec = do_div(delta, NSEC_PER_SEC);
-       set_normalized_timespec(&ts, wc_sec + delta, nsec);
-       /*
-        * Of all mechanisms of time adjustment I've tested, this one
-        * was the champion!
-        */
-       return ts.tv_sec + 1;
+       return ts.tv_sec;
 }
 
 static int kvm_set_wallclock(unsigned long now)
 {
-       return 0;
+       return -1;
 }
 
-/*
- * This is our read_clock function. The host puts an tsc timestamp each time
- * it updates a new time. Without the tsc adjustment, we can have a situation
- * in which a vcpu starts to run earlier (smaller system_time), but probes
- * time later (compared to another vcpu), leading to backwards time
- */
 static cycle_t kvm_clock_read(void)
 {
-       u64 last_tsc, now;
-       int cpu;
+       struct pvclock_vcpu_time_info *src;
+       cycle_t ret;
 
-       preempt_disable();
-       cpu = smp_processor_id();
-
-       last_tsc = get_clock(cpu, tsc_timestamp);
-       now = get_clock(cpu, system_time);
-
-       now += kvm_get_delta(last_tsc);
-       preempt_enable();
-
-       return now;
+       src = &get_cpu_var(hv_clock);
+       ret = pvclock_clocksource_read(src);
+       put_cpu_var(hv_clock);
+       return ret;
 }
+
 static struct clocksource kvm_clock = {
        .name = "kvm-clock",
        .read = kvm_clock_read,
@@ -123,13 +88,14 @@ static struct clocksource kvm_clock = {
        .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static int kvm_register_clock(void)
+static int kvm_register_clock(char *txt)
 {
        int cpu = smp_processor_id();
        int low, high;
        low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
        high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
-
+       printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
+              cpu, high, low, txt);
        return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
 }
 
@@ -140,12 +106,20 @@ static void kvm_setup_secondary_clock(void)
         * Now that the first cpu already had this clocksource initialized,
         * we shouldn't fail.
         */
-       WARN_ON(kvm_register_clock());
+       WARN_ON(kvm_register_clock("secondary cpu clock"));
        /* ok, done with our trickery, call native */
        setup_secondary_APIC_clock();
 }
 #endif
 
+#ifdef CONFIG_SMP
+void __init kvm_smp_prepare_boot_cpu(void)
+{
+       WARN_ON(kvm_register_clock("primary cpu clock"));
+       native_smp_prepare_boot_cpu();
+}
+#endif
+
 /*
  * After the clock is registered, the host will keep writing to the
  * registered memory location. If the guest happens to shutdown, this memory
@@ -174,13 +148,16 @@ void __init kvmclock_init(void)
                return;
 
        if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
-               if (kvm_register_clock())
+               if (kvm_register_clock("boot clock"))
                        return;
                pv_time_ops.get_wallclock = kvm_get_wallclock;
                pv_time_ops.set_wallclock = kvm_set_wallclock;
                pv_time_ops.sched_clock = kvm_clock_read;
 #ifdef CONFIG_X86_LOCAL_APIC
                pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
+#endif
+#ifdef CONFIG_SMP
+               smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 #endif
                machine_ops.shutdown  = kvm_shutdown;
 #ifdef CONFIG_KEXEC