On 07/14/2013 07:18 PM, Gleb Natapov wrote:

On Mon, Jun 24, 2013 at 06:13:04PM +0530, Raghavendra K T wrote:

quoted

kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

From: Srivatsa Vaddagiri <redacted>

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_pv_unhalt.

Signed-off-by: Srivatsa Vaddagiri <redacted>
Signed-off-by: Suzuki Poulose <redacted>
[Raghu: Apic related changes, folding pvunhalted into vcpu_runnable]
Signed-off-by: Raghavendra K T <redacted>
---
  arch/x86/include/asm/kvm_host.h      |    5 +++++
  arch/x86/include/uapi/asm/kvm_para.h |    1 +
  arch/x86/kvm/cpuid.c                 |    3 ++-
  arch/x86/kvm/x86.c                   |   37 ++++++++++++++++++++++++++++++++++
  include/uapi/linux/kvm_para.h        |    1 +
  5 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3741c65..95702de 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h

@@ -503,6 +503,11 @@ struct kvm_vcpu_arch {
  	 * instruction.
  	 */
  	bool write_fault_to_shadow_pgtable;
+
+	/* pv related host specific info */
+	struct {
+		bool pv_unhalted;
+	} pv;
  };

  struct kvm_lpage_info {

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 06fdbd9..94dc8ca 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h

@@ -23,6 +23,7 @@
  #define KVM_FEATURE_ASYNC_PF		4
  #define KVM_FEATURE_STEAL_TIME		5
  #define KVM_FEATURE_PV_EOI		6
+#define KVM_FEATURE_PV_UNHALT		7

  /* 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/cpuid.c b/arch/x86/kvm/cpuid.c
index a20ecb5..b110fe6 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c

@@ -413,7 +413,8 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
  			     (1 << KVM_FEATURE_CLOCKSOURCE2) |
  			     (1 << KVM_FEATURE_ASYNC_PF) |
  			     (1 << KVM_FEATURE_PV_EOI) |
-			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
+			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
+			     (1 << KVM_FEATURE_PV_UNHALT);

  		if (sched_info_on())
  			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 094b5d9..f8bea30 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c

@@ -5449,6 +5449,36 @@ 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) {
+		/*
+		 * Setting unhalt flag here can result in spurious runnable
+		 * state when unhalt reset does not happen in vcpu_block.
+		 * But that is harmless since that should soon result in halt.
+		 */
+		vcpu->arch.pv.pv_unhalted = true;
+		/* We need everybody see unhalt before vcpu unblocks */
+		smp_wmb();
+		kvm_vcpu_kick(vcpu);
+	}
+}
+
  int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
  {
  	unsigned long nr, a0, a1, a2, a3, ret;

@@ -5482,6 +5512,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
  	case KVM_HC_VAPIC_POLL_IRQ:
  		ret = 0;
  		break;
+	case KVM_HC_KICK_CPU:
+		kvm_pv_kick_cpu_op(vcpu->kvm, a0);

Lets make it hypercall with two parameters:
a0 - flags
a1 - apic id of a cpu to kick

A0 have to be zero. This will make it more extensible.

Good point. 'll incorporate that.