[Xen-devel] [PATCH RFC V9 13/19] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

[Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>]

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

From: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>

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 <vatsa@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Suzuki Poulose <suzuki@xxxxxxxxxx>
[Raghu: Apic related changes, folding pvunhalted into vcpu_runnable]
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
 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);
+               ret = 0;
+               break;
        default:
                ret = -KVM_ENOSYS;
                break;
@@ -5909,6 +5943,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
                                kvm_apic_accept_events(vcpu);
                                switch(vcpu->arch.mp_state) {
                                case KVM_MP_STATE_HALTED:
+                                       vcpu->arch.pv.pv_unhalted = false;
                                        vcpu->arch.mp_state =
                                                KVM_MP_STATE_RUNNABLE;
                                case KVM_MP_STATE_RUNNABLE:
@@ -6729,6 +6764,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
        BUG_ON(vcpu->kvm == NULL);
        kvm = vcpu->kvm;
 
+       vcpu->arch.pv.pv_unhalted = false;
        vcpu->arch.emulate_ctxt.ops = &emulate_ops;
        if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_bsp(vcpu))
                vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
@@ -7065,6 +7101,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
                !vcpu->arch.apf.halted)
                || !list_empty_careful(&vcpu->async_pf.done)
                || kvm_apic_has_events(vcpu)
+               || vcpu->arch.pv.pv_unhalted
                || atomic_read(&vcpu->arch.nmi_queued) ||
                (kvm_arch_interrupt_allowed(vcpu) &&
                 kvm_cpu_has_interrupt(vcpu));
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index cea2c5c..2841f86 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/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


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