| Message ID | 20130601192557.5966.12696.sendpatchset@codeblue (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jun 02, 2013 at 12:55:57AM +0530, Raghavendra K T wrote: > kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor > > From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> > > During smp_boot_cpus paravirtualied KVM guest detects if the hypervisor has > required feature (KVM_FEATURE_PV_UNHALT) to support pv-ticketlocks. If so, > support for pv-ticketlocks is registered via pv_lock_ops. > > Use KVM_HC_KICK_CPU hypercall to wakeup waiting/halted vcpu. > > Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> > Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com> > [Raghu: check_zero race fix, enum for kvm_contention_stat > jumplabel related changes ] > Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> > --- > arch/x86/include/asm/kvm_para.h | 14 ++ > arch/x86/kernel/kvm.c | 256 +++++++++++++++++++++++++++++++++++++++ > 2 files changed, 268 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index 695399f..427afcb 100644 > --- a/arch/x86/include/asm/kvm_para.h > +++ b/arch/x86/include/asm/kvm_para.h > @@ -118,10 +118,20 @@ void kvm_async_pf_task_wait(u32 token); > void kvm_async_pf_task_wake(u32 token); > u32 kvm_read_and_reset_pf_reason(void); > extern void kvm_disable_steal_time(void); > -#else > -#define kvm_guest_init() do { } while (0) > + > +#ifdef CONFIG_PARAVIRT_SPINLOCKS > +void __init kvm_spinlock_init(void); > +#else /* !CONFIG_PARAVIRT_SPINLOCKS */ > +static inline void kvm_spinlock_init(void) > +{ > +} > +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ > + > +#else /* CONFIG_KVM_GUEST */ > +#define kvm_guest_init() do {} while (0) > #define kvm_async_pf_task_wait(T) do {} while(0) > #define kvm_async_pf_task_wake(T) do {} while(0) > + > static inline u32 kvm_read_and_reset_pf_reason(void) > { > return 0; > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index cd6d9a5..2715b92 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -34,6 +34,7 @@ > #include <linux/sched.h> > #include <linux/slab.h> > #include <linux/kprobes.h> > +#include <linux/debugfs.h> > #include <asm/timer.h> > #include <asm/cpu.h> > #include <asm/traps.h> > @@ -419,6 +420,7 @@ static void __init kvm_smp_prepare_boot_cpu(void) > WARN_ON(kvm_register_clock("primary cpu clock")); > kvm_guest_cpu_init(); > native_smp_prepare_boot_cpu(); > + kvm_spinlock_init(); > } > > static void __cpuinit kvm_guest_cpu_online(void *dummy) > @@ -523,3 +525,257 @@ static __init int activate_jump_labels(void) > return 0; > } > arch_initcall(activate_jump_labels); > + > +/* Kick a cpu by its apicid. Used to wake up a halted vcpu */ > +void kvm_kick_cpu(int cpu) > +{ > + int apicid; > + > + apicid = per_cpu(x86_cpu_to_apicid, cpu); > + kvm_hypercall1(KVM_HC_KICK_CPU, apicid); > +} > + > +#ifdef CONFIG_PARAVIRT_SPINLOCKS > + > +enum kvm_contention_stat { > + TAKEN_SLOW, > + TAKEN_SLOW_PICKUP, > + RELEASED_SLOW, > + RELEASED_SLOW_KICKED, > + NR_CONTENTION_STATS > +}; > + > +#ifdef CONFIG_KVM_DEBUG_FS > +#define HISTO_BUCKETS 30 > + > +static struct kvm_spinlock_stats > +{ > + u32 contention_stats[NR_CONTENTION_STATS]; > + u32 histo_spin_blocked[HISTO_BUCKETS+1]; > + u64 time_blocked; > +} spinlock_stats; > + > +static u8 zero_stats; > + > +static inline void check_zero(void) > +{ > + u8 ret; > + u8 old; > + > + old = ACCESS_ONCE(zero_stats); > + if (unlikely(old)) { > + ret = cmpxchg(&zero_stats, old, 0); > + /* This ensures only one fellow resets the stat */ > + if (ret == old) > + memset(&spinlock_stats, 0, sizeof(spinlock_stats)); > + } > +} > + > +static inline void add_stats(enum kvm_contention_stat var, u32 val) > +{ > + check_zero(); > + spinlock_stats.contention_stats[var] += val; > +} > + > + > +static inline u64 spin_time_start(void) > +{ > + return sched_clock(); > +} > + > +static void __spin_time_accum(u64 delta, u32 *array) > +{ > + unsigned index; > + > + index = ilog2(delta); > + check_zero(); > + > + if (index < HISTO_BUCKETS) > + array[index]++; > + else > + array[HISTO_BUCKETS]++; > +} > + > +static inline void spin_time_accum_blocked(u64 start) > +{ > + u32 delta; > + > + delta = sched_clock() - start; > + __spin_time_accum(delta, spinlock_stats.histo_spin_blocked); > + spinlock_stats.time_blocked += delta; > +} > + > +static struct dentry *d_spin_debug; > +static struct dentry *d_kvm_debug; > + > +struct dentry *kvm_init_debugfs(void) > +{ > + d_kvm_debug = debugfs_create_dir("kvm", NULL); > + if (!d_kvm_debug) > + printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n"); > + > + return d_kvm_debug; > +} > + > +static int __init kvm_spinlock_debugfs(void) > +{ > + struct dentry *d_kvm; > + > + d_kvm = kvm_init_debugfs(); > + if (d_kvm == NULL) > + return -ENOMEM; > + > + d_spin_debug = debugfs_create_dir("spinlocks", d_kvm); > + > + debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats); > + > + debugfs_create_u32("taken_slow", 0444, d_spin_debug, > + &spinlock_stats.contention_stats[TAKEN_SLOW]); > + debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug, > + &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]); > + > + debugfs_create_u32("released_slow", 0444, d_spin_debug, > + &spinlock_stats.contention_stats[RELEASED_SLOW]); > + debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug, > + &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]); > + > + debugfs_create_u64("time_blocked", 0444, d_spin_debug, > + &spinlock_stats.time_blocked); > + > + debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug, > + spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1); > + > + return 0; > +} > +fs_initcall(kvm_spinlock_debugfs); > +#else /* !CONFIG_KVM_DEBUG_FS */ > +#define TIMEOUT (1 << 10) What do you use that for? > +static inline void add_stats(enum kvm_contention_stat var, u32 val) > +{ > +} > + > +static inline u64 spin_time_start(void) > +{ > + return 0; > +} > + > +static inline void spin_time_accum_blocked(u64 start) > +{ > +} > +#endif /* CONFIG_KVM_DEBUG_FS */ > + > +struct kvm_lock_waiting { > + struct arch_spinlock *lock; > + __ticket_t want; > +}; > + > +/* cpus 'waiting' on a spinlock to become available */ > +static cpumask_t waiting_cpus; > + > +/* Track spinlock on which a cpu is waiting */ > +static DEFINE_PER_CPU(struct kvm_lock_waiting, lock_waiting); > + > +static void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want) > +{ > + struct kvm_lock_waiting *w; > + int cpu; > + u64 start; > + unsigned long flags; > + > + w = &__get_cpu_var(lock_waiting); > + cpu = smp_processor_id(); > + start = spin_time_start(); > + > + /* > + * Make sure an interrupt handler can't upset things in a > + * partially setup state. > + */ > + local_irq_save(flags); > + > + /* > + * The ordering protocol on this is that the "lock" pointer > + * may only be set non-NULL if the "want" ticket is correct. > + * If we're updating "want", we must first clear "lock". > + */ > + w->lock = NULL; > + smp_wmb(); > + w->want = want; > + smp_wmb(); > + w->lock = lock; > + > + add_stats(TAKEN_SLOW, 1); > + > + /* > + * This uses set_bit, which is atomic but we should not rely on its > + * reordering gurantees. So barrier is needed after this call. > + */ > + cpumask_set_cpu(cpu, &waiting_cpus); > + > + barrier(); > + > + /* > + * Mark entry to slowpath before doing the pickup test to make > + * sure we don't deadlock with an unlocker. > + */ > + __ticket_enter_slowpath(lock); > + > + /* > + * check again make sure it didn't become free while > + * we weren't looking. > + */ > + if (ACCESS_ONCE(lock->tickets.head) == want) { > + add_stats(TAKEN_SLOW_PICKUP, 1); > + goto out; > + } > + > + /* Allow interrupts while blocked */ > + local_irq_restore(flags); > + > + /* halt until it's our turn and kicked. */ > + halt(); > + > + local_irq_save(flags); > +out: > + cpumask_clear_cpu(cpu, &waiting_cpus); > + w->lock = NULL; > + local_irq_restore(flags); > + spin_time_accum_blocked(start); > +} > +PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning); > + > +/* Kick vcpu waiting on @lock->head to reach value @ticket */ > +static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket) > +{ > + int cpu; > + > + add_stats(RELEASED_SLOW, 1); > + for_each_cpu(cpu, &waiting_cpus) { > + const struct kvm_lock_waiting *w = &per_cpu(lock_waiting, cpu); > + if (ACCESS_ONCE(w->lock) == lock && > + ACCESS_ONCE(w->want) == ticket) { > + add_stats(RELEASED_SLOW_KICKED, 1); > + kvm_kick_cpu(cpu); > + break; > + } > + } > +} > + > +/* > + * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. > + */ > +void __init kvm_spinlock_init(void) > +{ > + if (!kvm_para_available()) > + return; > + /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ > + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) > + return; > + > + printk(KERN_INFO"KVM setup paravirtual spinlock\n"); That spacing is odd. > + > + static_key_slow_inc(¶virt_ticketlocks_enabled); > + > + pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); > + pv_lock_ops.unlock_kick = kvm_unlock_kick; > +} > +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 06/03/2013 09:30 PM, Konrad Rzeszutek Wilk wrote: > On Sun, Jun 02, 2013 at 12:55:57AM +0530, Raghavendra K T wrote: >> kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor >> >> From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> >> >> During smp_boot_cpus paravirtualied KVM guest detects if the hypervisor has >> required feature (KVM_FEATURE_PV_UNHALT) to support pv-ticketlocks. If so, >> support for pv-ticketlocks is registered via pv_lock_ops. >> >> Use KVM_HC_KICK_CPU hypercall to wakeup waiting/halted vcpu. >> >> Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> >> Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com> >> [Raghu: check_zero race fix, enum for kvm_contention_stat >> jumplabel related changes ] >> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> >> --- >> arch/x86/include/asm/kvm_para.h | 14 ++ >> arch/x86/kernel/kvm.c | 256 +++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 268 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h >> index 695399f..427afcb 100644 >> --- a/arch/x86/include/asm/kvm_para.h >> +++ b/arch/x86/include/asm/kvm_para.h >> @@ -118,10 +118,20 @@ void kvm_async_pf_task_wait(u32 token); >> void kvm_async_pf_task_wake(u32 token); >> u32 kvm_read_and_reset_pf_reason(void); >> extern void kvm_disable_steal_time(void); >> -#else >> -#define kvm_guest_init() do { } while (0) >> + >> +#ifdef CONFIG_PARAVIRT_SPINLOCKS >> +void __init kvm_spinlock_init(void); >> +#else /* !CONFIG_PARAVIRT_SPINLOCKS */ >> +static inline void kvm_spinlock_init(void) >> +{ >> +} >> +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ >> + >> +#else /* CONFIG_KVM_GUEST */ >> +#define kvm_guest_init() do {} while (0) >> #define kvm_async_pf_task_wait(T) do {} while(0) >> #define kvm_async_pf_task_wake(T) do {} while(0) >> + >> static inline u32 kvm_read_and_reset_pf_reason(void) >> { >> return 0; >> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c >> index cd6d9a5..2715b92 100644 >> --- a/arch/x86/kernel/kvm.c >> +++ b/arch/x86/kernel/kvm.c >> @@ -34,6 +34,7 @@ >> #include <linux/sched.h> >> #include <linux/slab.h> >> #include <linux/kprobes.h> >> +#include <linux/debugfs.h> >> #include <asm/timer.h> >> #include <asm/cpu.h> >> #include <asm/traps.h> >> @@ -419,6 +420,7 @@ static void __init kvm_smp_prepare_boot_cpu(void) >> WARN_ON(kvm_register_clock("primary cpu clock")); >> kvm_guest_cpu_init(); >> native_smp_prepare_boot_cpu(); >> + kvm_spinlock_init(); >> } >> >> static void __cpuinit kvm_guest_cpu_online(void *dummy) >> @@ -523,3 +525,257 @@ static __init int activate_jump_labels(void) >> return 0; >> } >> arch_initcall(activate_jump_labels); >> + >> +/* Kick a cpu by its apicid. Used to wake up a halted vcpu */ >> +void kvm_kick_cpu(int cpu) >> +{ >> + int apicid; >> + >> + apicid = per_cpu(x86_cpu_to_apicid, cpu); >> + kvm_hypercall1(KVM_HC_KICK_CPU, apicid); >> +} >> + >> +#ifdef CONFIG_PARAVIRT_SPINLOCKS >> + >> +enum kvm_contention_stat { >> + TAKEN_SLOW, >> + TAKEN_SLOW_PICKUP, >> + RELEASED_SLOW, >> + RELEASED_SLOW_KICKED, >> + NR_CONTENTION_STATS >> +}; >> + >> +#ifdef CONFIG_KVM_DEBUG_FS >> +#define HISTO_BUCKETS 30 >> + >> +static struct kvm_spinlock_stats >> +{ >> + u32 contention_stats[NR_CONTENTION_STATS]; >> + u32 histo_spin_blocked[HISTO_BUCKETS+1]; >> + u64 time_blocked; >> +} spinlock_stats; >> + >> +static u8 zero_stats; >> + >> +static inline void check_zero(void) >> +{ >> + u8 ret; >> + u8 old; >> + >> + old = ACCESS_ONCE(zero_stats); >> + if (unlikely(old)) { >> + ret = cmpxchg(&zero_stats, old, 0); >> + /* This ensures only one fellow resets the stat */ >> + if (ret == old) >> + memset(&spinlock_stats, 0, sizeof(spinlock_stats)); >> + } >> +} >> + >> +static inline void add_stats(enum kvm_contention_stat var, u32 val) >> +{ >> + check_zero(); >> + spinlock_stats.contention_stats[var] += val; >> +} >> + >> + >> +static inline u64 spin_time_start(void) >> +{ >> + return sched_clock(); >> +} >> + >> +static void __spin_time_accum(u64 delta, u32 *array) >> +{ >> + unsigned index; >> + >> + index = ilog2(delta); >> + check_zero(); >> + >> + if (index < HISTO_BUCKETS) >> + array[index]++; >> + else >> + array[HISTO_BUCKETS]++; >> +} >> + >> +static inline void spin_time_accum_blocked(u64 start) >> +{ >> + u32 delta; >> + >> + delta = sched_clock() - start; >> + __spin_time_accum(delta, spinlock_stats.histo_spin_blocked); >> + spinlock_stats.time_blocked += delta; >> +} >> + >> +static struct dentry *d_spin_debug; >> +static struct dentry *d_kvm_debug; >> + >> +struct dentry *kvm_init_debugfs(void) >> +{ >> + d_kvm_debug = debugfs_create_dir("kvm", NULL); >> + if (!d_kvm_debug) >> + printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n"); >> + >> + return d_kvm_debug; >> +} >> + >> +static int __init kvm_spinlock_debugfs(void) >> +{ >> + struct dentry *d_kvm; >> + >> + d_kvm = kvm_init_debugfs(); >> + if (d_kvm == NULL) >> + return -ENOMEM; >> + >> + d_spin_debug = debugfs_create_dir("spinlocks", d_kvm); >> + >> + debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats); >> + >> + debugfs_create_u32("taken_slow", 0444, d_spin_debug, >> + &spinlock_stats.contention_stats[TAKEN_SLOW]); >> + debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug, >> + &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]); >> + >> + debugfs_create_u32("released_slow", 0444, d_spin_debug, >> + &spinlock_stats.contention_stats[RELEASED_SLOW]); >> + debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug, >> + &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]); >> + >> + debugfs_create_u64("time_blocked", 0444, d_spin_debug, >> + &spinlock_stats.time_blocked); >> + >> + debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug, >> + spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1); >> + >> + return 0; >> +} >> +fs_initcall(kvm_spinlock_debugfs); >> +#else /* !CONFIG_KVM_DEBUG_FS */ >> +#define TIMEOUT (1 << 10) > > What do you use that for? > > Thanks Konrad for the review. Great eyes! .. will remove this in next patch. >> +static inline void add_stats(enum kvm_contention_stat var, u32 val) >> +{ >> +} >> + >> +static inline u64 spin_time_start(void) >> +{ >> + return 0; >> +} >> + >> +static inline void spin_time_accum_blocked(u64 start) >> +{ >> +} >> +#endif /* CONFIG_KVM_DEBUG_FS */ >> + >> +struct kvm_lock_waiting { >> + struct arch_spinlock *lock; >> + __ticket_t want; >> +}; >> + >> +/* cpus 'waiting' on a spinlock to become available */ >> +static cpumask_t waiting_cpus; >> + >> +/* Track spinlock on which a cpu is waiting */ >> +static DEFINE_PER_CPU(struct kvm_lock_waiting, lock_waiting); >> + >> +static void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want) >> +{ >> + struct kvm_lock_waiting *w; >> + int cpu; >> + u64 start; >> + unsigned long flags; >> + >> + w = &__get_cpu_var(lock_waiting); >> + cpu = smp_processor_id(); >> + start = spin_time_start(); >> + >> + /* >> + * Make sure an interrupt handler can't upset things in a >> + * partially setup state. >> + */ >> + local_irq_save(flags); >> + >> + /* >> + * The ordering protocol on this is that the "lock" pointer >> + * may only be set non-NULL if the "want" ticket is correct. >> + * If we're updating "want", we must first clear "lock". >> + */ >> + w->lock = NULL; >> + smp_wmb(); >> + w->want = want; >> + smp_wmb(); >> + w->lock = lock; >> + >> + add_stats(TAKEN_SLOW, 1); >> + >> + /* >> + * This uses set_bit, which is atomic but we should not rely on its >> + * reordering gurantees. So barrier is needed after this call. >> + */ >> + cpumask_set_cpu(cpu, &waiting_cpus); >> + >> + barrier(); >> + >> + /* >> + * Mark entry to slowpath before doing the pickup test to make >> + * sure we don't deadlock with an unlocker. >> + */ >> + __ticket_enter_slowpath(lock); >> + >> + /* >> + * check again make sure it didn't become free while >> + * we weren't looking. >> + */ >> + if (ACCESS_ONCE(lock->tickets.head) == want) { >> + add_stats(TAKEN_SLOW_PICKUP, 1); >> + goto out; >> + } >> + >> + /* Allow interrupts while blocked */ >> + local_irq_restore(flags); >> + >> + /* halt until it's our turn and kicked. */ >> + halt(); >> + >> + local_irq_save(flags); >> +out: >> + cpumask_clear_cpu(cpu, &waiting_cpus); >> + w->lock = NULL; >> + local_irq_restore(flags); >> + spin_time_accum_blocked(start); >> +} >> +PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning); >> + >> +/* Kick vcpu waiting on @lock->head to reach value @ticket */ >> +static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket) >> +{ >> + int cpu; >> + >> + add_stats(RELEASED_SLOW, 1); >> + for_each_cpu(cpu, &waiting_cpus) { >> + const struct kvm_lock_waiting *w = &per_cpu(lock_waiting, cpu); >> + if (ACCESS_ONCE(w->lock) == lock && >> + ACCESS_ONCE(w->want) == ticket) { >> + add_stats(RELEASED_SLOW_KICKED, 1); >> + kvm_kick_cpu(cpu); >> + break; >> + } >> + } >> +} >> + >> +/* >> + * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. >> + */ >> +void __init kvm_spinlock_init(void) >> +{ >> + if (!kvm_para_available()) >> + return; >> + /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ >> + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) >> + return; >> + >> + printk(KERN_INFO"KVM setup paravirtual spinlock\n"); > > That spacing is odd. Yes. Will modify in the next version. > >> + >> + static_key_slow_inc(¶virt_ticketlocks_enabled); >> + >> + pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); >> + pv_lock_ops.unlock_kick = kvm_unlock_kick; >> +} >> +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ >> > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 695399f..427afcb 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -118,10 +118,20 @@ void kvm_async_pf_task_wait(u32 token); void kvm_async_pf_task_wake(u32 token); u32 kvm_read_and_reset_pf_reason(void); extern void kvm_disable_steal_time(void); -#else -#define kvm_guest_init() do { } while (0) + +#ifdef CONFIG_PARAVIRT_SPINLOCKS +void __init kvm_spinlock_init(void); +#else /* !CONFIG_PARAVIRT_SPINLOCKS */ +static inline void kvm_spinlock_init(void) +{ +} +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ + +#else /* CONFIG_KVM_GUEST */ +#define kvm_guest_init() do {} while (0) #define kvm_async_pf_task_wait(T) do {} while(0) #define kvm_async_pf_task_wake(T) do {} while(0) + static inline u32 kvm_read_and_reset_pf_reason(void) { return 0; diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index cd6d9a5..2715b92 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -34,6 +34,7 @@ #include <linux/sched.h> #include <linux/slab.h> #include <linux/kprobes.h> +#include <linux/debugfs.h> #include <asm/timer.h> #include <asm/cpu.h> #include <asm/traps.h> @@ -419,6 +420,7 @@ static void __init kvm_smp_prepare_boot_cpu(void) WARN_ON(kvm_register_clock("primary cpu clock")); kvm_guest_cpu_init(); native_smp_prepare_boot_cpu(); + kvm_spinlock_init(); } static void __cpuinit kvm_guest_cpu_online(void *dummy) @@ -523,3 +525,257 @@ static __init int activate_jump_labels(void) return 0; } arch_initcall(activate_jump_labels); + +/* Kick a cpu by its apicid. Used to wake up a halted vcpu */ +void kvm_kick_cpu(int cpu) +{ + int apicid; + + apicid = per_cpu(x86_cpu_to_apicid, cpu); + kvm_hypercall1(KVM_HC_KICK_CPU, apicid); +} + +#ifdef CONFIG_PARAVIRT_SPINLOCKS + +enum kvm_contention_stat { + TAKEN_SLOW, + TAKEN_SLOW_PICKUP, + RELEASED_SLOW, + RELEASED_SLOW_KICKED, + NR_CONTENTION_STATS +}; + +#ifdef CONFIG_KVM_DEBUG_FS +#define HISTO_BUCKETS 30 + +static struct kvm_spinlock_stats +{ + u32 contention_stats[NR_CONTENTION_STATS]; + u32 histo_spin_blocked[HISTO_BUCKETS+1]; + u64 time_blocked; +} spinlock_stats; + +static u8 zero_stats; + +static inline void check_zero(void) +{ + u8 ret; + u8 old; + + old = ACCESS_ONCE(zero_stats); + if (unlikely(old)) { + ret = cmpxchg(&zero_stats, old, 0); + /* This ensures only one fellow resets the stat */ + if (ret == old) + memset(&spinlock_stats, 0, sizeof(spinlock_stats)); + } +} + +static inline void add_stats(enum kvm_contention_stat var, u32 val) +{ + check_zero(); + spinlock_stats.contention_stats[var] += val; +} + + +static inline u64 spin_time_start(void) +{ + return sched_clock(); +} + +static void __spin_time_accum(u64 delta, u32 *array) +{ + unsigned index; + + index = ilog2(delta); + check_zero(); + + if (index < HISTO_BUCKETS) + array[index]++; + else + array[HISTO_BUCKETS]++; +} + +static inline void spin_time_accum_blocked(u64 start) +{ + u32 delta; + + delta = sched_clock() - start; + __spin_time_accum(delta, spinlock_stats.histo_spin_blocked); + spinlock_stats.time_blocked += delta; +} + +static struct dentry *d_spin_debug; +static struct dentry *d_kvm_debug; + +struct dentry *kvm_init_debugfs(void) +{ + d_kvm_debug = debugfs_create_dir("kvm", NULL); + if (!d_kvm_debug) + printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n"); + + return d_kvm_debug; +} + +static int __init kvm_spinlock_debugfs(void) +{ + struct dentry *d_kvm; + + d_kvm = kvm_init_debugfs(); + if (d_kvm == NULL) + return -ENOMEM; + + d_spin_debug = debugfs_create_dir("spinlocks", d_kvm); + + debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats); + + debugfs_create_u32("taken_slow", 0444, d_spin_debug, + &spinlock_stats.contention_stats[TAKEN_SLOW]); + debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug, + &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]); + + debugfs_create_u32("released_slow", 0444, d_spin_debug, + &spinlock_stats.contention_stats[RELEASED_SLOW]); + debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug, + &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]); + + debugfs_create_u64("time_blocked", 0444, d_spin_debug, + &spinlock_stats.time_blocked); + + debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug, + spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1); + + return 0; +} +fs_initcall(kvm_spinlock_debugfs); +#else /* !CONFIG_KVM_DEBUG_FS */ +#define TIMEOUT (1 << 10) +static inline void add_stats(enum kvm_contention_stat var, u32 val) +{ +} + +static inline u64 spin_time_start(void) +{ + return 0; +} + +static inline void spin_time_accum_blocked(u64 start) +{ +} +#endif /* CONFIG_KVM_DEBUG_FS */ + +struct kvm_lock_waiting { + struct arch_spinlock *lock; + __ticket_t want; +}; + +/* cpus 'waiting' on a spinlock to become available */ +static cpumask_t waiting_cpus; + +/* Track spinlock on which a cpu is waiting */ +static DEFINE_PER_CPU(struct kvm_lock_waiting, lock_waiting); + +static void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want) +{ + struct kvm_lock_waiting *w; + int cpu; + u64 start; + unsigned long flags; + + w = &__get_cpu_var(lock_waiting); + cpu = smp_processor_id(); + start = spin_time_start(); + + /* + * Make sure an interrupt handler can't upset things in a + * partially setup state. + */ + local_irq_save(flags); + + /* + * The ordering protocol on this is that the "lock" pointer + * may only be set non-NULL if the "want" ticket is correct. + * If we're updating "want", we must first clear "lock". + */ + w->lock = NULL; + smp_wmb(); + w->want = want; + smp_wmb(); + w->lock = lock; + + add_stats(TAKEN_SLOW, 1); + + /* + * This uses set_bit, which is atomic but we should not rely on its + * reordering gurantees. So barrier is needed after this call. + */ + cpumask_set_cpu(cpu, &waiting_cpus); + + barrier(); + + /* + * Mark entry to slowpath before doing the pickup test to make + * sure we don't deadlock with an unlocker. + */ + __ticket_enter_slowpath(lock); + + /* + * check again make sure it didn't become free while + * we weren't looking. + */ + if (ACCESS_ONCE(lock->tickets.head) == want) { + add_stats(TAKEN_SLOW_PICKUP, 1); + goto out; + } + + /* Allow interrupts while blocked */ + local_irq_restore(flags); + + /* halt until it's our turn and kicked. */ + halt(); + + local_irq_save(flags); +out: + cpumask_clear_cpu(cpu, &waiting_cpus); + w->lock = NULL; + local_irq_restore(flags); + spin_time_accum_blocked(start); +} +PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning); + +/* Kick vcpu waiting on @lock->head to reach value @ticket */ +static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket) +{ + int cpu; + + add_stats(RELEASED_SLOW, 1); + for_each_cpu(cpu, &waiting_cpus) { + const struct kvm_lock_waiting *w = &per_cpu(lock_waiting, cpu); + if (ACCESS_ONCE(w->lock) == lock && + ACCESS_ONCE(w->want) == ticket) { + add_stats(RELEASED_SLOW_KICKED, 1); + kvm_kick_cpu(cpu); + break; + } + } +} + +/* + * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. + */ +void __init kvm_spinlock_init(void) +{ + if (!kvm_para_available()) + return; + /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) + return; + + printk(KERN_INFO"KVM setup paravirtual spinlock\n"); + + static_key_slow_inc(¶virt_ticketlocks_enabled); + + pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); + pv_lock_ops.unlock_kick = kvm_unlock_kick; +} +#endif /* CONFIG_PARAVIRT_SPINLOCKS */