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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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