Add two hypercalls to KVM hypervisor to support pv-ticketlocks.
KVM_HC_WAIT_FOR_KICK blocks the calling vcpu until another vcpu kicks it or it
is woken up because of an event like interrupt.
KVM_HC_KICK_CPU allows the calling vcpu to kick another vcpu.
The presence of these hypercalls is indicated to guest via
KVM_FEATURE_WAIT_FOR_KICK/KVM_CAP_WAIT_FOR_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.
There is no Xen/KVM hypercall interface to await kick from.
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..2874c19 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_WAIT_FOR_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 84a28ea..b43fd18 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2077,6 +2077,7 @@ 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_WAIT_FOR_KICK:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -2548,7 +2549,8 @@ 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_WAIT_FOR_KICK);
if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
@@ -5231,6 +5233,61 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
return 1;
}
+/*
+ * kvm_pv_wait_for_kick_op : Block until kicked by either a KVM_HC_KICK_CPU
+ * hypercall or a event like interrupt.
+ *
+ * @vcpu : vcpu which is blocking.
+ */
+static void kvm_pv_wait_for_kick_op(struct kvm_vcpu *vcpu)
+{
+ DEFINE_WAIT(wait);
+
+ /*
+ * Blocking on vcpu->wq allows us to wake up sooner if required to
+ * service pending events (like interrupts).
+ *
+ * Also set state to TASK_INTERRUPTIBLE before checking vcpu->kicked to
+ * avoid racing with kvm_pv_kick_cpu_op().
+ */
+ prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
+
+ /*
+ * Somebody has already tried kicking us. Acknowledge that
+ * and terminate the wait.
+ */
+ if (vcpu->kicked) {
+ vcpu->kicked = 0;
+ goto end_wait;
+ }
+
+ /* Let's wait for either KVM_HC_KICK_CPU or someother event
+ * to wake us up.
+ */
+
+ srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
+ schedule();
+ vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+
+end_wait:
+ finish_wait(&vcpu->wq, &wait);
+}
+
+/*
+ * 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);
+
+ if (vcpu) {
+ vcpu->kicked = 1;
+ wake_up_interruptible(&vcpu->wq);
+ }
+}
+
int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
{
unsigned long nr, a0, a1, a2, a3, ret;
@@ -5267,6 +5324,14 @@ 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_WAIT_FOR_KICK:
+ kvm_pv_wait_for_kick_op(vcpu);
+ ret = 0;
+ 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 aace6b8..736acc0 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -553,6 +553,7 @@ struct kvm_ppc_pvinfo {
#define KVM_CAP_SPAPR_TCE 63
#define KVM_CAP_PPC_SMT 64
#define KVM_CAP_PPC_RMA 65
+#define KVM_CAP_WAIT_FOR_KICK 66
#define KVM_CAP_S390_GMAP 71
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index eabb21a..2946563 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -152,6 +152,11 @@ 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..4efee4d 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -19,6 +19,8 @@
#define KVM_HC_MMU_OP 2
#define KVM_HC_FEATURES 3
#define KVM_HC_PPC_MAP_MAGIC_PAGE 4
+#define KVM_HC_WAIT_FOR_KICK 5
+#define KVM_HC_KICK_CPU 6
/*
* hypercalls use architecture specific
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index aefdda3..d09982d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -224,6 +224,7 @@ 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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