| Message ID | 1559799086-13912-2-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: LAPIC: Implement Exitless Timer | expand |
2019-06-06 13:31+0800, Wanpeng Li: > From: Wanpeng Li <wanpengli@tencent.com> > > Make lapic timer unpinned when timer is injected by posted-interrupt, > the emulated timer can be offload to the housekeeping cpus. > > The host admin should fine tuned, e.g. dedicated instances scenario > w/ nohz_full cover the pCPUs which vCPUs resident, several pCPUs > surplus for housekeeping, disable mwait/hlt/pause vmexits to occupy > the pCPUs, fortunately preemption timer is disabled after mwait is > exposed to guest which makes emulated timer offload can be possible. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/kvm/lapic.c | 20 ++++++++++++++++---- > arch/x86/kvm/x86.c | 5 +++++ > arch/x86/kvm/x86.h | 2 ++ > include/linux/sched/isolation.h | 2 ++ > kernel/sched/isolation.c | 6 ++++++ > 5 files changed, 31 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index fcf42a3..09b7387 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -127,6 +127,12 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) > return apic->vcpu->vcpu_id; > } > > +static inline bool posted_interrupt_inject_timer_enabled(struct kvm_vcpu *vcpu) > +{ > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && > + kvm_mwait_in_guest(vcpu->kvm); I'm torn about the mwait dependency. It covers a lot of the targeted user base, but the relation is convoluted and not fitting perfectly. What do you think about making posted_interrupt_inject_timer_enabled() just pi_inject_timer && kvm_vcpu_apicv_active(vcpu) and disarming the vmx preemption timer when posted_interrupt_inject_timer_enabled(), just like we do with mwait now? Thanks.
On Tue, 11 Jun 2019 at 01:11, Radim Krčmář <rkrcmar@redhat.com> wrote: > > 2019-06-06 13:31+0800, Wanpeng Li: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > Make lapic timer unpinned when timer is injected by posted-interrupt, > > the emulated timer can be offload to the housekeeping cpus. > > > > The host admin should fine tuned, e.g. dedicated instances scenario > > w/ nohz_full cover the pCPUs which vCPUs resident, several pCPUs > > surplus for housekeeping, disable mwait/hlt/pause vmexits to occupy > > the pCPUs, fortunately preemption timer is disabled after mwait is > > exposed to guest which makes emulated timer offload can be possible. > > > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Radim Krčmář <rkrcmar@redhat.com> > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > > --- > > arch/x86/kvm/lapic.c | 20 ++++++++++++++++---- > > arch/x86/kvm/x86.c | 5 +++++ > > arch/x86/kvm/x86.h | 2 ++ > > include/linux/sched/isolation.h | 2 ++ > > kernel/sched/isolation.c | 6 ++++++ > > 5 files changed, 31 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > > index fcf42a3..09b7387 100644 > > --- a/arch/x86/kvm/lapic.c > > +++ b/arch/x86/kvm/lapic.c > > @@ -127,6 +127,12 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) > > return apic->vcpu->vcpu_id; > > } > > > > +static inline bool posted_interrupt_inject_timer_enabled(struct kvm_vcpu *vcpu) > > +{ > > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && > > + kvm_mwait_in_guest(vcpu->kvm); > > I'm torn about the mwait dependency. It covers a lot of the targeted > user base, but the relation is convoluted and not fitting perfectly. > > What do you think about making posted_interrupt_inject_timer_enabled() > just > > pi_inject_timer && kvm_vcpu_apicv_active(vcpu) > > and disarming the vmx preemption timer when > posted_interrupt_inject_timer_enabled(), just like we do with mwait now? Agreed, thanks for the review. :) Regards, Wanpeng Li
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index fcf42a3..09b7387 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -127,6 +127,12 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) return apic->vcpu->vcpu_id; } +static inline bool posted_interrupt_inject_timer_enabled(struct kvm_vcpu *vcpu) +{ + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && + kvm_mwait_in_guest(vcpu->kvm); +} + static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map, u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) { switch (map->mode) { @@ -1581,7 +1587,9 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic) likely(ns > apic->lapic_timer.timer_advance_ns)) { expire = ktime_add_ns(now, ns); expire = ktime_sub_ns(expire, ktimer->timer_advance_ns); - hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS_PINNED); + hrtimer_start(&ktimer->timer, expire, + posted_interrupt_inject_timer_enabled(vcpu) ? + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED); } else apic_timer_expired(apic); @@ -1683,7 +1691,8 @@ static void start_sw_period(struct kvm_lapic *apic) hrtimer_start(&apic->lapic_timer.timer, apic->lapic_timer.target_expiration, - HRTIMER_MODE_ABS_PINNED); + posted_interrupt_inject_timer_enabled(apic->vcpu) ? + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED); } bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu) @@ -2320,7 +2329,8 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns) apic->vcpu = vcpu; hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC, - HRTIMER_MODE_ABS_PINNED); + posted_interrupt_inject_timer_enabled(vcpu) ? + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED); apic->lapic_timer.timer.function = apic_timer_fn; if (timer_advance_ns == -1) { apic->lapic_timer.timer_advance_ns = 1000; @@ -2509,7 +2519,9 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu) timer = &vcpu->arch.apic->lapic_timer.timer; if (hrtimer_cancel(timer)) - hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED); + hrtimer_start_expires(timer, + posted_interrupt_inject_timer_enabled(vcpu) ? + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED); } /* diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6200d5a..2ef2394 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -54,6 +54,7 @@ #include <linux/kvm_irqfd.h> #include <linux/irqbypass.h> #include <linux/sched/stat.h> +#include <linux/sched/isolation.h> #include <linux/mem_encrypt.h> #include <trace/events/kvm.h> @@ -155,6 +156,9 @@ EXPORT_SYMBOL_GPL(enable_vmware_backdoor); static bool __read_mostly force_emulation_prefix = false; module_param(force_emulation_prefix, bool, S_IRUGO); +bool __read_mostly pi_inject_timer = 0; +module_param(pi_inject_timer, bool, S_IRUGO | S_IWUSR); + #define KVM_NR_SHARED_MSRS 16 struct kvm_shared_msrs_global { @@ -7030,6 +7034,7 @@ int kvm_arch_init(void *opaque) host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK); kvm_lapic_init(); + pi_inject_timer = housekeeping_enabled(HK_FLAG_TIMER); #ifdef CONFIG_X86_64 pvclock_gtod_register_notifier(&pvclock_gtod_notifier); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 275b3b6..aa539d6 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -296,6 +296,8 @@ extern unsigned int min_timer_period_us; extern bool enable_vmware_backdoor; +extern bool pi_inject_timer; + extern struct static_key kvm_no_apic_vcpu; static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec) diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h index b0fb144..6fc5407 100644 --- a/include/linux/sched/isolation.h +++ b/include/linux/sched/isolation.h @@ -19,6 +19,7 @@ enum hk_flags { DECLARE_STATIC_KEY_FALSE(housekeeping_overridden); extern int housekeeping_any_cpu(enum hk_flags flags); extern const struct cpumask *housekeeping_cpumask(enum hk_flags flags); +extern bool housekeeping_enabled(enum hk_flags flags); extern void housekeeping_affine(struct task_struct *t, enum hk_flags flags); extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags); extern void __init housekeeping_init(void); @@ -38,6 +39,7 @@ static inline const struct cpumask *housekeeping_cpumask(enum hk_flags flags) static inline void housekeeping_affine(struct task_struct *t, enum hk_flags flags) { } static inline void housekeeping_init(void) { } +static inline bool housekeeping_enabled(enum hk_flags flags) { } #endif /* CONFIG_CPU_ISOLATION */ static inline bool housekeeping_cpu(int cpu, enum hk_flags flags) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 123ea07..ccb2808 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -14,6 +14,12 @@ EXPORT_SYMBOL_GPL(housekeeping_overridden); static cpumask_var_t housekeeping_mask; static unsigned int housekeeping_flags; +bool housekeeping_enabled(enum hk_flags flags) +{ + return !!(housekeeping_flags & flags); +} +EXPORT_SYMBOL_GPL(housekeeping_enabled); + int housekeeping_any_cpu(enum hk_flags flags) { if (static_branch_unlikely(&housekeeping_overridden))