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

[Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>]

On 07/14/2013 07:18 PM, Gleb Natapov wrote:
> 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.
Good point. 'll incorporate that.



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