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Re: [Xen-devel] [PATCH RFC V10 12/18] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks



On Mon, Jun 24, 2013 at 06:13:04PM +0530, Raghavendra K T wrote:
> kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks
> 
> From: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>
> 
> kvm_hc_kick_cpu allows the calling vcpu to kick another vcpu out of halt 
> state.
> the presence of these hypercalls is indicated to guest via
> kvm_feature_pv_unhalt.
> 
> Signed-off-by: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Suzuki Poulose <suzuki@xxxxxxxxxx>
> [Raghu: Apic related changes, folding pvunhalted into vcpu_runnable]
> Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h      |    5 +++++
>  arch/x86/include/uapi/asm/kvm_para.h |    1 +
>  arch/x86/kvm/cpuid.c                 |    3 ++-
>  arch/x86/kvm/x86.c                   |   37 
> ++++++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm_para.h        |    1 +
>  5 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 3741c65..95702de 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -503,6 +503,11 @@ struct kvm_vcpu_arch {
>        * instruction.
>        */
>       bool write_fault_to_shadow_pgtable;
> +
> +     /* pv related host specific info */
> +     struct {
> +             bool pv_unhalted;
> +     } pv;
>  };
>  
>  struct kvm_lpage_info {
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h 
> b/arch/x86/include/uapi/asm/kvm_para.h
> index 06fdbd9..94dc8ca 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -23,6 +23,7 @@
>  #define KVM_FEATURE_ASYNC_PF         4
>  #define KVM_FEATURE_STEAL_TIME               5
>  #define KVM_FEATURE_PV_EOI           6
> +#define KVM_FEATURE_PV_UNHALT                7
>  
>  /* The last 8 bits are used to indicate how to interpret the flags field
>   * in pvclock structure. If no bits are set, all flags are ignored.
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index a20ecb5..b110fe6 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -413,7 +413,8 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, 
> u32 function,
>                            (1 << KVM_FEATURE_CLOCKSOURCE2) |
>                            (1 << KVM_FEATURE_ASYNC_PF) |
>                            (1 << KVM_FEATURE_PV_EOI) |
> -                          (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> +                          (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> +                          (1 << KVM_FEATURE_PV_UNHALT);
>  
>               if (sched_info_on())
>                       entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 094b5d9..f8bea30 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5449,6 +5449,36 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>       return 1;
>  }
>  
> +/*
> + * kvm_pv_kick_cpu_op:  Kick a vcpu.
> + *
> + * @apicid - apicid of vcpu to be kicked.
> + */
> +static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
> +{
> +     struct kvm_vcpu *vcpu = NULL;
> +     int i;
> +
> +     kvm_for_each_vcpu(i, vcpu, kvm) {
> +             if (!kvm_apic_present(vcpu))
> +                     continue;
> +
> +             if (kvm_apic_match_dest(vcpu, 0, 0, apicid, 0))
> +                     break;
> +     }
> +     if (vcpu) {
> +             /*
> +              * Setting unhalt flag here can result in spurious runnable
> +              * state when unhalt reset does not happen in vcpu_block.
> +              * But that is harmless since that should soon result in halt.
> +              */
> +             vcpu->arch.pv.pv_unhalted = true;
> +             /* We need everybody see unhalt before vcpu unblocks */
> +             smp_wmb();
> +             kvm_vcpu_kick(vcpu);
> +     }
> +}
> +
>  int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>  {
>       unsigned long nr, a0, a1, a2, a3, ret;
> @@ -5482,6 +5512,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>       case KVM_HC_VAPIC_POLL_IRQ:
>               ret = 0;
>               break;
> +     case KVM_HC_KICK_CPU:
> +             kvm_pv_kick_cpu_op(vcpu->kvm, a0);
Lets make it hypercall with two parameters: 
a0 - flags
a1 - apic id of a cpu to kick

A0 have to be zero. This will make it more extensible.

> +             ret = 0;
> +             break;
>       default:
>               ret = -KVM_ENOSYS;
>               break;
> @@ -5909,6 +5943,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>                               kvm_apic_accept_events(vcpu);
>                               switch(vcpu->arch.mp_state) {
>                               case KVM_MP_STATE_HALTED:
> +                                     vcpu->arch.pv.pv_unhalted = false;
>                                       vcpu->arch.mp_state =
>                                               KVM_MP_STATE_RUNNABLE;
>                               case KVM_MP_STATE_RUNNABLE:
> @@ -6729,6 +6764,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>       BUG_ON(vcpu->kvm == NULL);
>       kvm = vcpu->kvm;
>  
> +     vcpu->arch.pv.pv_unhalted = false;
>       vcpu->arch.emulate_ctxt.ops = &emulate_ops;
>       if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_bsp(vcpu))
>               vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> @@ -7065,6 +7101,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>               !vcpu->arch.apf.halted)
>               || !list_empty_careful(&vcpu->async_pf.done)
>               || kvm_apic_has_events(vcpu)
> +             || vcpu->arch.pv.pv_unhalted
>               || atomic_read(&vcpu->arch.nmi_queued) ||
>               (kvm_arch_interrupt_allowed(vcpu) &&
>                kvm_cpu_has_interrupt(vcpu));
> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> index cea2c5c..2841f86 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -19,6 +19,7 @@
>  #define KVM_HC_MMU_OP                        2
>  #define KVM_HC_FEATURES                      3
>  #define KVM_HC_PPC_MAP_MAGIC_PAGE    4
> +#define KVM_HC_KICK_CPU                      5
I wounder why hypercalls are not defined in architecture headers.

--
                        Gleb.

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