[PATCH 2/4] Make xen use the generic paravirt clocksource code.

Gerd Hoffmann
2008-04-24T08:37:06Z

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
arch/x86/xen/Kconfig | 1 +
arch/x86/xen/time.c | 110 +++++---------------------------------------------
2 files changed, 12 insertions(+), 99 deletions(-)

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 4d5f264..47f0cdc 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -5,6 +5,7 @@
config XEN
bool "Xen guest support"
select PARAVIRT
+ select PARAVIRT_CLOCK
depends on X86_32
depends on X86_CMPXCHG && X86_TSC && !NEED_MULTIPLE_NODES && !(X86_VISWS || X86_VOYAGER)
help
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) {
--
1.5.4.1