From 7af192c954017499ec163bc9dbaaee2e593d7ef2 Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann Date: Tue, 3 Jun 2008 16:17:29 +0200 Subject: x86: Add structs and functions for paravirt clocksource This patch adds structs for the paravirt clocksource ABI used by both xen and kvm (pvclock-abi.h). It also adds some helper functions to read system time and wall clock time from a paravirtual clocksource (pvclock.[ch]). They are based on the xen code. They are enabled using CONFIG_PARAVIRT_CLOCK. Subsequent patches of this series will put the code in use. Signed-off-by: Gerd Hoffmann Acked-by: Jeremy Fitzhardinge Signed-off-by: Avi Kivity --- arch/x86/kernel/Makefile | 1 + arch/x86/kernel/pvclock.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 142 insertions(+) create mode 100644 arch/x86/kernel/pvclock.c (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 5e618c3b4720..77807d4769c9 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -82,6 +82,7 @@ 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_CLOCK) += pvclock.o obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c new file mode 100644 index 000000000000..05fbe9a0325a --- /dev/null +++ b/arch/x86/kernel/pvclock.c @@ -0,0 +1,141 @@ +/* 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 +#include +#include + +/* + * 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; +}; + +/* + * 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 pvclock_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; +} + +cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) +{ + struct pvclock_shadow_time shadow; + unsigned version; + cycle_t ret, offset; + + do { + version = pvclock_get_time_values(&shadow, src); + barrier(); + offset = pvclock_get_nsec_offset(&shadow); + ret = shadow.system_timestamp + offset; + barrier(); + } while (version != src->version); + + return ret; +} + +void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, + struct pvclock_vcpu_time_info *vcpu_time, + struct timespec *ts) +{ + u32 version; + u64 delta; + struct timespec now; + + /* get wallclock at system boot */ + do { + version = wall_clock->version; + rmb(); /* fetch version before time */ + now.tv_sec = wall_clock->sec; + now.tv_nsec = wall_clock->nsec; + rmb(); /* fetch time before checking version */ + } while ((wall_clock->version & 1) || (version != wall_clock->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); +} -- cgit v1.2.3 From f6e16d5ad463d15f285666f588cfe49495c692d9 Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann Date: Tue, 3 Jun 2008 16:17:32 +0200 Subject: 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 Signed-off-by: Avi Kivity --- arch/x86/kernel/kvmclock.c | 89 +++++++++++++++++----------------------------- 1 file changed, 33 insertions(+), 56 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 08a30986d472..87edf1ceb1df 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -18,6 +18,7 @@ #include #include +#include #include #include #include @@ -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 -- cgit v1.2.3