[Xen-devel] [PATCH RFC V8 13/17] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

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

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>
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |    4 ++++
 arch/x86/include/asm/kvm_para.h |    2 ++
 arch/x86/kvm/cpuid.c            |    3 ++-
 arch/x86/kvm/x86.c              |   37 +++++++++++++++++++++++++++++++++++++
 include/linux/kvm_para.h        |    1 +
 5 files changed, 46 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e216ba0..e187a9b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -481,6 +481,10 @@ struct kvm_vcpu_arch {
                u64 length;
                u64 status;
        } osvw;
+       /* pv related host specific info */
+       struct {
+               bool pv_unhalted;
+       } pv;
 };
 
 struct kvm_lpage_info {
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 734c376..5b647ea 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_PV_UNHALT          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/cpuid.c b/arch/x86/kvm/cpuid.c
index 9fed5be..7c93806 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -408,7 +408,8 @@ static int 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_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 91a5e98..f188cdc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4993,6 +4993,36 @@ 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;
@@ -5026,6 +5056,10 @@ 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;
@@ -5409,6 +5443,7 @@ static int __vcpu_run(struct kvm_vcpu *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:
@@ -6128,6 +6163,7 @@ 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;
@@ -6394,6 +6430,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
                !vcpu->arch.apf.halted)
                || !list_empty_careful(&vcpu->async_pf.done)
                || vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
+               || 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/linux/kvm_para.h b/include/linux/kvm_para.h
index ff476dd..38226e1 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


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