Re: [PATCH RFC V4 2/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

On 01/16/2012 08:54 AM, Alexander Graf wrote:

On 14.01.2012, at 19:25, Raghavendra K T wrote:

quoted

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_PVLOCK_KICK/KVM_CAP_PVLOCK_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.

Signed-off-by: Srivatsa Vaddagiri<redacted>
Signed-off-by: Suzuki Poulose<redacted>
Signed-off-by: Raghavendra K T<redacted>
---

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 734c376..7a94987 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_PVLOCK_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 4c938da..c7b05fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c

@@ -2099,6 +2099,7 @@ 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_PVLOCK_KICK:
		r = 1;
		break;
	case KVM_CAP_COALESCED_MMIO:

@@ -2576,7 +2577,8 @@ 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_PVLOCK_KICK);

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

@@ -5304,6 +5306,29 @@ 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) {
+		kvm_make_request(KVM_REQ_PVLOCK_KICK, vcpu);
+		kvm_vcpu_kick(vcpu);
+	}
+}
+
int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
{
	unsigned long nr, a0, a1, a2, a3, ret;

@@ -5340,6 +5365,10 @@ 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 68e67e5..63fb6b0 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h

@@ -558,6 +558,7 @@ struct kvm_ppc_pvinfo {

#define KVM_CAP_PPC_PAPR 68
#define KVM_CAP_S390_GMAP 71
#define KVM_CAP_TSC_DEADLINE_TIMER 72
+#define KVM_CAP_PVLOCK_KICK 73

#ifdef KVM_CAP_IRQ_ROUTING

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d526231..3b1ae7b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h

@@ -50,6 +50,7 @@

#define KVM_REQ_APF_HALT          12
#define KVM_REQ_STEAL_UPDATE      13
#define KVM_REQ_NMI               14
+#define KVM_REQ_PVLOCK_KICK       15

Everything I see in this patch is pvlock agnostic. It's only a vcpu kick hypercall. So it's probably a good idea to also name it accordingly :).


Alex

It was indeed KICK_VCPU in V4. But since we are currently dealing with
only pv locks it is renamed so.  But if we start using the code for
flush_tlb_others_ipi() optimization etc, it is good idea to rename
accordingly. OR even  go back to KICK_VCPU as used earlier..

 - Raghu