From: Gleb Natapov <[email protected]>

Windows issues this hypercall after guest was spinning on a spinlock
for too many iterations.

Signed-off-by: Gleb Natapov <[email protected]>
Signed-off-by: Vadim Rozenfeld <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 22eb3f0..47c6e23 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1565,6 +1565,7 @@ int kvm_dev_ioctl_check_extension(long ext)
        case KVM_CAP_VCPU_EVENTS:
        case KVM_CAP_HYPERV:
        case KVM_CAP_HYPERV_VAPIC:
+       case KVM_CAP_HYPERV_SPIN:
                r = 1;
                break;
        case KVM_CAP_COALESCED_MMIO:
@@ -3828,7 +3829,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
        trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
-       res = HV_STATUS_INVALID_HYPERCALL_CODE;
+       switch (code) {
+       case HV_X64_HV_NOTIFY_LONG_SPIN_WAIT:
+               kvm_vcpu_on_spin(vcpu);
+               break;
+       default:
+               res = HV_STATUS_INVALID_HYPERCALL_CODE;
+               break;
+       }
 
        ret = res | (((u64)rep_done & 0xfff) << 32);
        if (longmode) {
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 5ce6173..4c4937e 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -499,6 +499,7 @@ struct kvm_ioeventfd {
 #define KVM_CAP_PPC_SEGSTATE 43
 #define KVM_CAP_HYPERV 44
 #define KVM_CAP_HYPERV_VAPIC 45
+#define KVM_CAP_HYPERV_SPIN 46
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
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