Jeremy Fitzhardinge wrote:
> Gerd Hoffmann wrote:
>> +cycle_t pvclock_clocksource_read(struct kvm_vcpu_time_info *src)
>> +{
>> + struct pvclock_shadow_time *shadow = &get_cpu_var(shadow_time);
>> + cycle_t ret;
>> +
>> + pvclock_get_time_values(shadow, src);
>> + ret = shadow->system_timestamp + pvclock_get_nsec_offset(shadow);
>>
>
> You need to put this in a loop in case the system clock parameters
> change between the pvclock_get_time_values() and pvclock_get_nsec_offset().
Fixed, new patch attached.
> How does kvm deal with suspend/resume with respect to time? Is the
> "system" timestamp guaranteed to remain monotonic? For Xen, I think
> we'll need to maintain an offset between the initial system timestamp
> and whatever it is after resuming.
Havn't looked at it yet.
cheers,
Gerd
--
http://kraxel.fedorapeople.org/xenner/
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 1cc9d42..688df87 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -79,7 +79,7 @@ obj-$(CONFIG_DEBUG_NX_TEST) += test_nx.o
obj-$(CONFIG_VMI) += vmi_32.o vmiclock_32.o
obj-$(CONFIG_KVM_GUEST) += kvm.o
obj-$(CONFIG_KVM_CLOCK) += kvmclock.o
-obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o
+obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o pvclock.o
ifdef CONFIG_INPUT_PCSPKR
obj-y += pcspeaker.o
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index ddee040..476b7c7 100644
--- 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>
@@ -37,17 +38,9 @@ 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 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
@@ -55,35 +48,19 @@ static cycle_t kvm_clock_read(void);
*/
unsigned long kvm_get_wallclock(void)
{
- u32 wc_sec, wc_nsec;
- u64 delta;
+ struct kvm_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);
-
- delta = kvm_clock_read();
-
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;
+
+ vcpu_time = &get_cpu_var(hv_clock);
+ pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
+ put_cpu_var(hv_clock);
+
+ return ts.tv_sec;
}
int kvm_set_wallclock(unsigned long now)
@@ -91,28 +68,17 @@ int kvm_set_wallclock(unsigned long now)
return 0;
}
-/*
- * 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 kvm_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,
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
new file mode 100644
index 0000000..6e7dae0
--- /dev/null
+++ b/arch/x86/kernel/pvclock.c
@@ -0,0 +1,150 @@
+/* paravirtual clock -- common code used by kvm/xen
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#include <linux/kernel.h>
+#include <linux/percpu.h>
+#include <asm/pvclock.h>
+
+/*
+ * These are perodically updated
+ * xen: magic shared_info page
+ * kvm: gpa registered via msr
+ * and then copied here.
+ */
+struct pvclock_shadow_time {
+ u64 tsc_timestamp; /* TSC at last update of time vals. */
+ u64 system_timestamp; /* Time, in nanosecs, since boot. */
+ u32 tsc_to_nsec_mul;
+ int tsc_shift;
+ u32 version;
+};
+
+static DEFINE_PER_CPU(struct pvclock_shadow_time, shadow_time);
+
+/*
+ * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
+ * yielding a 64-bit result.
+ */
+static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
+{
+ u64 product;
+#ifdef __i386__
+ u32 tmp1, tmp2;
+#endif
+
+ if (shift < 0)
+ delta >>= -shift;
+ else
+ delta <<= shift;
+
+#ifdef __i386__
+ __asm__ (
+ "mul %5 ; "
+ "mov %4,%%eax ; "
+ "mov %%edx,%4 ; "
+ "mul %5 ; "
+ "xor %5,%5 ; "
+ "add %4,%%eax ; "
+ "adc %5,%%edx ; "
+ : "=A" (product), "=r" (tmp1), "=r" (tmp2)
+ : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
+#elif __x86_64__
+ __asm__ (
+ "mul %%rdx ; shrd $32,%%rdx,%%rax"
+ : "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
+#else
+#error implement me!
+#endif
+
+ return product;
+}
+
+static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
+{
+ u64 delta = native_read_tsc() - shadow->tsc_timestamp;
+ return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
+}
+
+/*
+ * Reads a consistent set of time-base values from hypervisor,
+ * into a shadow data area.
+ */
+static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
+ struct kvm_vcpu_time_info *src)
+{
+ do {
+ dst->version = src->version;
+ rmb(); /* fetch version before data */
+ dst->tsc_timestamp = src->tsc_timestamp;
+ dst->system_timestamp = src->system_time;
+ dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
+ dst->tsc_shift = src->tsc_shift;
+ rmb(); /* test version after fetching data */
+ } while ((src->version & 1) | (dst->version ^ src->version));
+
+ return dst->version;
+}
+
+/*
+ * 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
+ */
+cycle_t pvclock_clocksource_read(struct kvm_vcpu_time_info *src)
+{
+ struct pvclock_shadow_time *shadow;
+ cycle_t ret;
+ unsigned version;
+
+ shadow = &get_cpu_var(shadow_time);
+ do {
+ version = pvclock_get_time_values(shadow, src);
+ barrier();
+ ret = shadow->system_timestamp + pvclock_get_nsec_offset(shadow);
+ barrier();
+ } while (version != src->version);
+
+ put_cpu_var(shadow_time);
+ return ret;
+}
+
+void pvclock_read_wallclock(struct kvm_wall_clock *wall_clock,
+ struct kvm_vcpu_time_info *vcpu_time,
+ struct timespec *ts)
+{
+ u32 version;
+ u64 delta;
+ struct timespec now;
+
+ /* get wallclock at system boot */
+ do {
+ version = wall_clock->wc_version;
+ rmb(); /* fetch version before time */
+ now.tv_sec = wall_clock->wc_sec;
+ now.tv_nsec = wall_clock->wc_nsec;
+ rmb(); /* fetch time before checking version */
+ } while ((wall_clock->wc_version & 1) || (version != wall_clock->wc_version));
+
+ delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
+ delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
+
+ now.tv_nsec = do_div(delta, NSEC_PER_SEC);
+ now.tv_sec = delta;
+
+ set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
+}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0ce5563..bdd3128 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -493,7 +493,7 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
{
static int version;
struct kvm_wall_clock wc;
- struct timespec wc_ts;
+ struct timespec now,sys,boot;
if (!wall_clock)
return;
@@ -502,9 +502,16 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
- wc_ts = current_kernel_time();
- wc.wc_sec = wc_ts.tv_sec;
- wc.wc_nsec = wc_ts.tv_nsec;
+#if 0
+ /* Hmm, getboottime() isn't exported to modules ... */
+ getboottime(&boot);
+#else
+ now = current_kernel_time();
+ ktime_get_ts(&sys);
+ boot = ns_to_timespec(timespec_to_ns(&now) - timespec_to_ns(&sys));
+#endif
+ wc.wc_sec = boot.tv_sec;
+ wc.wc_nsec = boot.tv_nsec;
wc.wc_version = version;
kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc));
@@ -544,13 +551,51 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
- sizeof(vcpu->hv_clock));
+ sizeof(vcpu->hv_clock));
kunmap_atomic(shared_kaddr, KM_USER0);
mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
}
+static uint32_t div_frac(uint32_t dividend, uint32_t divisor)
+{
+ uint32_t quotient, remainder;
+
+ __asm__ ( "divl %4"
+ : "=a" (quotient), "=d" (remainder)
+ : "0" (0), "1" (dividend), "r" (divisor) );
+ return quotient;
+}
+
+static void kvm_set_time_scale(uint32_t tsc_khz, struct kvm_vcpu_time_info *hv_clock)
+{
+ uint64_t nsecs = 1000000000LL;
+ int32_t shift = 0;
+ uint64_t tps64;
+ uint32_t tps32;
+
+ tps64 = tsc_khz * 1000LL;
+ while (tps64 > nsecs*2) {
+ tps64 >>= 1;
+ shift--;
+ }
+
+ tps32 = (uint32_t)tps64;
+ while (tps32 <= (uint32_t)nsecs) {
+ tps32 <<= 1;
+ shift++;
+ }
+
+ hv_clock->tsc_shift = shift;
+ hv_clock->tsc_to_system_mul = div_frac(nsecs, tps32);
+
+#if 0
+ printk(KERN_DEBUG "%s: tsc_khz %u, tsc_shift %d, tsc_mul %u\n",
+ __FUNCTION__, tsc_khz, hv_clock->tsc_shift,
+ hv_clock->tsc_to_system_mul);
+#endif
+}
int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
@@ -599,9 +644,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
/* ...but clean it before doing the actual write */
vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
- vcpu->arch.hv_clock.tsc_to_system_mul =
- clocksource_khz2mult(tsc_khz, 22);
- vcpu->arch.hv_clock.tsc_shift = 22;
+ kvm_set_time_scale(tsc_khz, &vcpu->arch.hv_clock);
down_read(¤t->mm->mmap_sem);
vcpu->arch.time_page =
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c39e1a5..3d5f945 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -13,6 +13,7 @@
#include <linux/clockchips.h>
#include <linux/kernel_stat.h>
+#include <asm/pvclock.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
@@ -30,17 +31,6 @@
static cycle_t xen_clocksource_read(void);
-/* These are perodically updated in shared_info, and then copied here. */
-struct shadow_time_info {
- u64 tsc_timestamp; /* TSC at last update of time vals. */
- u64 system_timestamp; /* Time, in nanosecs, since boot. */
- u32 tsc_to_nsec_mul;
- int tsc_shift;
- u32 version;
-};
-
-static DEFINE_PER_CPU(struct shadow_time_info, shadow_time);
-
/* runstate info updated by Xen */
static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);
@@ -230,95 +220,14 @@ unsigned long xen_cpu_khz(void)
return xen_khz;
}
-/*
- * Reads a consistent set of time-base values from Xen, into a shadow data
- * area.
- */
-static unsigned get_time_values_from_xen(void)
-{
- struct vcpu_time_info *src;
- struct shadow_time_info *dst;
-
- /* src is shared memory with the hypervisor, so we need to
- make sure we get a consistent snapshot, even in the face of
- being preempted. */
- src = &__get_cpu_var(xen_vcpu)->time;
- dst = &__get_cpu_var(shadow_time);
-
- do {
- dst->version = src->version;
- rmb(); /* fetch version before data */
- dst->tsc_timestamp = src->tsc_timestamp;
- dst->system_timestamp = src->system_time;
- dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
- dst->tsc_shift = src->tsc_shift;
- rmb(); /* test version after fetching data */
- } while ((src->version & 1) | (dst->version ^ src->version));
-
- return dst->version;
-}
-
-/*
- * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
- * yielding a 64-bit result.
- */
-static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
-{
- u64 product;
-#ifdef __i386__
- u32 tmp1, tmp2;
-#endif
-
- if (shift < 0)
- delta >>= -shift;
- else
- delta <<= shift;
-
-#ifdef __i386__
- __asm__ (
- "mul %5 ; "
- "mov %4,%%eax ; "
- "mov %%edx,%4 ; "
- "mul %5 ; "
- "xor %5,%5 ; "
- "add %4,%%eax ; "
- "adc %5,%%edx ; "
- : "=A" (product), "=r" (tmp1), "=r" (tmp2)
- : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
-#elif __x86_64__
- __asm__ (
- "mul %%rdx ; shrd $32,%%rdx,%%rax"
- : "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
-#else
-#error implement me!
-#endif
-
- return product;
-}
-
-static u64 get_nsec_offset(struct shadow_time_info *shadow)
-{
- u64 now, delta;
- now = native_read_tsc();
- delta = now - shadow->tsc_timestamp;
- return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
-}
-
static cycle_t xen_clocksource_read(void)
{
- struct shadow_time_info *shadow = &get_cpu_var(shadow_time);
+ struct vcpu_time_info *src;
cycle_t ret;
- unsigned version;
-
- do {
- version = get_time_values_from_xen();
- barrier();
- ret = shadow->system_timestamp + get_nsec_offset(shadow);
- barrier();
- } while (version != __get_cpu_var(xen_vcpu)->time.version);
-
- put_cpu_var(shadow_time);
+ src = &get_cpu_var(xen_vcpu)->time;
+ ret = pvclock_clocksource_read((void*)src);
+ put_cpu_var(xen_vcpu);
return ret;
}
@@ -349,9 +258,14 @@ static void xen_read_wallclock(struct timespec *ts)
unsigned long xen_get_wallclock(void)
{
+ const struct shared_info *s = HYPERVISOR_shared_info;
+ struct kvm_wall_clock *wall_clock = (void*)&(s->wc_version);
+ struct vcpu_time_info *vcpu_time;
struct timespec ts;
- xen_read_wallclock(&ts);
+ vcpu_time = &get_cpu_var(xen_vcpu)->time;
+ pvclock_read_wallclock(wall_clock, (void*)vcpu_time, &ts);
+ put_cpu_var(xen_vcpu);
return ts.tv_sec;
}
@@ -576,8 +490,6 @@ __init void xen_time_init(void)
{
int cpu = smp_processor_id();
- get_time_values_from_xen();
-
clocksource_register(&xen_clocksource);
if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
diff --git a/include/asm-x86/pvclock.h b/include/asm-x86/pvclock.h
new file mode 100644
index 0000000..2b9812f
--- /dev/null
+++ b/include/asm-x86/pvclock.h
@@ -0,0 +1,6 @@
+#include <linux/clocksource.h>
+#include <asm/kvm_para.h>
+cycle_t pvclock_clocksource_read(struct kvm_vcpu_time_info *src);
+void pvclock_read_wallclock(struct kvm_wall_clock *wall,
+ struct kvm_vcpu_time_info *vcpu,
+ struct timespec *ts);
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