Re: [Xen-devel] [PATCH RFC V4 2/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

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

On 01/16/2012 08:54 AM, Alexander Graf wrote:
> On 14.01.2012, at 19:25, Raghavendra K T wrote:
>
> > Add a hypercall to KVM hypervisor to support pv-ticketlocks
> >
> > 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_PVLOCK_KICK/KVM_CAP_PVLOCK_KICK.
> >
> > Qemu needs a corresponding patch to pass up the presence of this feature to
> > guest via cpuid. Patch to qemu will be sent separately.
> >
> > Signed-off-by: Srivatsa Vaddagiri<vatsa@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Suzuki Poulose<suzuki@xxxxxxxxxx>
> > Signed-off-by: Raghavendra K T<raghavendra.kt@xxxxxxxxxxxxxxxxxx>
> > ---
> > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
> > index 734c376..7a94987 100644
> > --- a/arch/x86/include/asm/kvm_para.h
> > +++ b/arch/x86/include/asm/kvm_para.h
> > @@ -16,12 +16,14 @@
> > #define KVM_FEATURE_CLOCKSOURCE         0
> > #define KVM_FEATURE_NOP_IO_DELAY        1
> > #define KVM_FEATURE_MMU_OP              2
> > +
> > /* This indicates that the new set of kvmclock msrs
> >   * are available. The use of 0x11 and 0x12 is deprecated
> >   */
> > #define KVM_FEATURE_CLOCKSOURCE2        3
> > #define KVM_FEATURE_ASYNC_PF            4
> > #define KVM_FEATURE_STEAL_TIME          5
> > +#define KVM_FEATURE_PVLOCK_KICK                6
> >
> > /* 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/x86.c b/arch/x86/kvm/x86.c
> > index 4c938da..c7b05fc 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2099,6 +2099,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> >         case KVM_CAP_XSAVE:
> >         case KVM_CAP_ASYNC_PF:
> >         case KVM_CAP_GET_TSC_KHZ:
> > +       case KVM_CAP_PVLOCK_KICK:
> >                 r = 1;
> >                 break;
> >         case KVM_CAP_COALESCED_MMIO:
> > @@ -2576,7 +2577,8 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, 
> > u32 function,
> >                              (1<<  KVM_FEATURE_NOP_IO_DELAY) |
> >                              (1<<  KVM_FEATURE_CLOCKSOURCE2) |
> >                              (1<<  KVM_FEATURE_ASYNC_PF) |
> > -                            (1<<  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> > +                            (1<<  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> > +                            (1<<  KVM_FEATURE_PVLOCK_KICK);
> >
> >                 if (sched_info_on())
> >                         entry->eax |= (1<<  KVM_FEATURE_STEAL_TIME);
> > @@ -5304,6 +5306,29 @@ 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) {
> > +               kvm_make_request(KVM_REQ_PVLOCK_KICK, vcpu);
> > +               kvm_vcpu_kick(vcpu);
> > +       }
> > +}
> > +
> > int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> > {
> >         unsigned long nr, a0, a1, a2, a3, ret;
> > @@ -5340,6 +5365,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> >         case KVM_HC_MMU_OP:
> >                 r = kvm_pv_mmu_op(vcpu, a0, hc_gpa(vcpu, a1, a2),&ret);
> >                 break;
> > +       case KVM_HC_KICK_CPU:
> > +               kvm_pv_kick_cpu_op(vcpu->kvm, a0);
> > +               ret = 0;
> > +               break;
> >         default:
> >                 ret = -KVM_ENOSYS;
> >                 break;
> > diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> > index 68e67e5..63fb6b0 100644
> > --- a/include/linux/kvm.h
> > +++ b/include/linux/kvm.h
> > @@ -558,6 +558,7 @@ struct kvm_ppc_pvinfo {
> > #define KVM_CAP_PPC_PAPR 68
> > #define KVM_CAP_S390_GMAP 71
> > #define KVM_CAP_TSC_DEADLINE_TIMER 72
> > +#define KVM_CAP_PVLOCK_KICK 73
> >
> > #ifdef KVM_CAP_IRQ_ROUTING
> >
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index d526231..3b1ae7b 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -50,6 +50,7 @@
> > #define KVM_REQ_APF_HALT          12
> > #define KVM_REQ_STEAL_UPDATE      13
> > #define KVM_REQ_NMI               14
> > +#define KVM_REQ_PVLOCK_KICK       15
> Everything I see in this patch is pvlock agnostic. It's only a vcpu kick 
> hypercall. So it's probably a good idea to also name it accordingly :).
>
>
> Alex
It was indeed KICK_VCPU in V4. But since we are currently dealing with
only pv locks it is renamed so.  But if we start using the code for
flush_tlb_others_ipi() optimization etc, it is good idea to rename
accordingly. OR even  go back to KICK_VCPU as used earlier..

 - Raghu


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