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    Subject[PATCH RFC V3 2/4] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks
    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_KICK_VCPU/KVM_CAP_KICK_VCPU.

    Qemu needs a corresponding patch to pass up the presence of this feature to
    guest via cpuid. Patch to qemu will be sent separately.

    There is no Xen/KVM hypercall interface to await kick from.

    Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
    Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com>
    Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
    ---
    diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
    index 734c376..8b1d65d 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_KICK_VCPU 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 c38efd7..6e1c8b4 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -2103,6 +2103,7 @@ 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_KICK_VCPU:
    r = 1;
    break;
    case KVM_CAP_COALESCED_MMIO:
    @@ -2577,7 +2578,8 @@ 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_KICK_VCPU);

    if (sched_info_on())
    entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
    @@ -5305,6 +5307,26 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
    return 1;
    }

    +/*
    + * kvm_pv_kick_cpu_op: Kick a vcpu.
    + *
    + * @cpu - vcpu to be kicked.
    + */
    +static void kvm_pv_kick_cpu_op(struct kvm *kvm, int cpu)
    +{
    + struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, cpu);
    + struct kvm_mp_state mp_state;
    +
    + mp_state.mp_state = KVM_MP_STATE_RUNNABLE;
    + if (vcpu) {
    + vcpu->kicked = 1;
    + /* Ensure kicked is always set before wakeup */
    + barrier();
    + }
    + kvm_arch_vcpu_ioctl_set_mpstate(vcpu, &mp_state);
    + kvm_vcpu_kick(vcpu);
    +}
    +
    int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
    {
    unsigned long nr, a0, a1, a2, a3, ret;
    @@ -5341,6 +5363,10 @@ 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 f47fcd3..e760035 100644
    --- a/include/linux/kvm.h
    +++ b/include/linux/kvm.h
    @@ -558,6 +558,7 @@ struct kvm_ppc_pvinfo {
    #define KVM_CAP_PPC_HIOR 67
    #define KVM_CAP_PPC_PAPR 68
    #define KVM_CAP_S390_GMAP 71
    +#define KVM_CAP_KICK_VCPU 72

    #ifdef KVM_CAP_IRQ_ROUTING

    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index d526231..ff3b6ff 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -154,6 +154,11 @@ struct kvm_vcpu {
    #endif

    struct kvm_vcpu_arch arch;
    +
    + /*
    + * blocked vcpu wakes up by checking this flag set by unlocker.
    + */
    + int kicked;
    };

    static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
    diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
    index 47a070b..19f10bd 100644
    --- a/include/linux/kvm_para.h
    +++ b/include/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

    /*
    * hypercalls use architecture specific
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index d9cfb78..8f4b6db 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -226,6 +226,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
    vcpu->kvm = kvm;
    vcpu->vcpu_id = id;
    vcpu->pid = NULL;
    + vcpu->kicked = 0;
    init_waitqueue_head(&vcpu->wq);
    kvm_async_pf_vcpu_init(vcpu);



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