flush_tlb_others_ipi depends on lot of statics in tlb.c. Replicated the flush_tlb_others_ipi as kvm_flush_tlb_others to further adapt to paravirtualization. Use the vcpu state information inside the kvm_flush_tlb_others to avoid sending ipi to pre-empted vcpus. * Do not send ipi's to offline vcpus and set flush_on_enter flag * For online vcpus: Wait for them to clear the flag The approach was discussed here: https://lkml.org/lkml/2012/2/20/157 Suggested-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Signed-off-by: Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx> -- Pseudo Algo: Write() ====== guest_exit() flush_on_enter[i]=0; running[i] = 0; guest_enter() running[i] = 1; smp_mb(); if(flush_on_enter[i]) { tlb_flush() flush_on_enter[i]=0; } Read() ====== GUEST KVM-HV f->flushcpumask = cpumask - me; again: for_each_cpu(i, f->flushmask) { if (!running[i]) { case 1: running[n]=1 (cpuN does not see flush_on_enter set, guest later finds it running and sends ipi, we are fine here, need to clear the flag on guest_exit) flush_on_enter[i] = 1; case2: running[n]=1 (cpuN - will see flush on enter and an IPI as well - addressed in patch-4) if (!running[i]) cpu_clear(f->flushmask); All is well, vm_enter will do the fixup } case 3: running[n] = 0; (cpuN went to sleep, we saw it as awake, ipi sent, but wait will break without zero_mask and goto again will take care) } send_ipi(f->flushmask) wait_a_while_for_zero_mask(); if (!zero_mask) goto again; --- arch/x86/include/asm/kvm_para.h | 3 +- arch/x86/include/asm/tlbflush.h | 9 ++++++ arch/x86/kernel/kvm.c | 1 + arch/x86/kvm/x86.c | 14 ++++++++- arch/x86/mm/tlb.c | 61 +++++++++++++++++++++++++++++++++++++++ 5 files changed, 86 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index f57b5cc..684a285 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -55,7 +55,8 @@ struct kvm_steal_time { struct kvm_vcpu_state { __u32 state; - __u32 pad[15]; + __u32 flush_on_enter; + __u32 pad[14]; }; #define KVM_VCPU_STATE_ALIGN_BITS 5 diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index c0e108e..29470bd 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -119,6 +119,12 @@ static inline void native_flush_tlb_others(const struct cpumask *cpumask, { } +static inline void kvm_flush_tlb_others(const struct cpumask *cpumask, + struct mm_struct *mm, + unsigned long va) +{ +} + static inline void reset_lazy_tlbstate(void) { } @@ -145,6 +151,9 @@ static inline void flush_tlb_range(struct vm_area_struct *vma, void native_flush_tlb_others(const struct cpumask *cpumask, struct mm_struct *mm, unsigned long va); +void kvm_flush_tlb_others(const struct cpumask *cpumask, + struct mm_struct *mm, unsigned long va); + #define TLBSTATE_OK 1 #define TLBSTATE_LAZY 2 diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index bb686a6..66db54e 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -465,6 +465,7 @@ void __init kvm_guest_init(void) } has_vcpu_state = 1; + pv_mmu_ops.flush_tlb_others = kvm_flush_tlb_others; #ifdef CONFIG_SMP smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 264f172..4714a7b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1548,9 +1548,20 @@ static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu) if (!(vcpu->arch.v_state.msr_val & KVM_MSR_ENABLED)) return; + /* + * Let the guest know that we are online, make sure we do not + * overwrite flush_on_enter, just write the vs->state. + */ vs->state = 1; - kvm_write_guest_cached(vcpu->kvm, ghc, vs, 2*sizeof(__u32)); + kvm_write_guest_cached(vcpu->kvm, ghc, vs, 1*sizeof(__u32)); smp_wmb(); + /* + * Guest might have seen us offline and would have set + * flush_on_enter. + */ + kvm_read_guest_cached(vcpu->kvm, ghc, vs, 2*sizeof(__u32)); + if (vs->flush_on_enter) + kvm_x86_ops->tlb_flush(vcpu); } static void kvm_clear_vcpu_state(struct kvm_vcpu *vcpu) @@ -1561,6 +1572,7 @@ static void kvm_clear_vcpu_state(struct kvm_vcpu *vcpu) if (!(vcpu->arch.v_state.msr_val & KVM_MSR_ENABLED)) return; + vs->flush_on_enter = 0; vs->state = 0; kvm_write_guest_cached(vcpu->kvm, ghc, vs, 2*sizeof(__u32)); smp_wmb(); diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index d6c0418..f5dacdd 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -6,6 +6,7 @@ #include <linux/interrupt.h> #include <linux/module.h> #include <linux/cpu.h> +#include <linux/kvm_para.h> #include <asm/tlbflush.h> #include <asm/mmu_context.h> @@ -202,6 +203,66 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask, raw_spin_unlock(&f->tlbstate_lock); } +#ifdef CONFIG_KVM_GUEST + +DECLARE_PER_CPU(struct kvm_vcpu_state, vcpu_state) __aligned(64); + +void kvm_flush_tlb_others(const struct cpumask *cpumask, + struct mm_struct *mm, unsigned long va) +{ + unsigned int sender; + union smp_flush_state *f; + int cpu, loop; + struct kvm_vcpu_state *v_state; + + /* Caller has disabled preemption */ + sender = this_cpu_read(tlb_vector_offset); + f = &flush_state[sender]; + + if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS) + raw_spin_lock(&f->tlbstate_lock); + + f->flush_mm = mm; + f->flush_va = va; + if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) { + /* + * We have to send the IPI only to online vCPUs + * affected. And queue flush_on_enter for pre-empted + * vCPUs + */ +again: + for_each_cpu(cpu, to_cpumask(f->flush_cpumask)) { + v_state = &per_cpu(vcpu_state, cpu); + + if (!v_state->state) { + v_state->flush_on_enter = 1; + smp_mb(); + if (!v_state->state) + cpumask_clear_cpu(cpu, to_cpumask(f->flush_cpumask)); + } + } + + if (cpumask_empty(to_cpumask(f->flush_cpumask))) + goto out; + + apic->send_IPI_mask(to_cpumask(f->flush_cpumask), + INVALIDATE_TLB_VECTOR_START + sender); + + loop = 1000; + while (!cpumask_empty(to_cpumask(f->flush_cpumask)) && --loop) + cpu_relax(); + + if (!cpumask_empty(to_cpumask(f->flush_cpumask))) + goto again; + } +out: + f->flush_mm = NULL; + f->flush_va = 0; + if (nr_cpu_ids > NUM_INVALIDATE_TLB_VECTORS) + raw_spin_unlock(&f->tlbstate_lock); +} +#endif /* CONFIG_KVM_GUEST */ + void native_flush_tlb_others(const struct cpumask *cpumask, struct mm_struct *mm, unsigned long va) { -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
