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[Xen-devel] [PATCH RFC V5 2/6] 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/KVM_CAP_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>
---
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 734c376..9234f13 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.
@@ -32,6 +34,7 @@
 #define MSR_KVM_SYSTEM_TIME 0x12
 
 #define KVM_MSR_ENABLED 1
+
 /* Custom MSRs falls in the range 0x4b564d00-0x4b564dff */
 #define MSR_KVM_WALL_CLOCK_NEW  0x4b564d00
 #define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 89b02bf..61388b9 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 9cbfc06..bd5ef91 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2079,6 +2079,7 @@ 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_PV_UNHALT:
                r = 1;
                break;
        case KVM_CAP_COALESCED_MMIO:
@@ -4913,6 +4914,30 @@ 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) {
+               vcpu->pv_unhalted = 1;
+               smp_mb();
+               kvm_vcpu_kick(vcpu);
+       }
+}
+
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 {
        unsigned long nr, a0, a1, a2, a3, ret;
@@ -4946,6 +4971,10 @@ 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;
@@ -6174,6 +6203,7 @@ 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->pv_unhalted
                || atomic_read(&vcpu->arch.nmi_queued) ||
                (kvm_arch_interrupt_allowed(vcpu) &&
                 kvm_cpu_has_interrupt(vcpu));
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 68e67e5..e822d96 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_PV_UNHALT 73
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 900c763..433ae97 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -158,6 +158,7 @@ struct kvm_vcpu {
 #endif
 
        struct kvm_vcpu_arch arch;
+       int pv_unhalted;
 };
 
 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 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
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a91f980..d3b98b1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -226,6 +226,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, 
unsigned id)
        vcpu->kvm = kvm;
        vcpu->vcpu_id = id;
        vcpu->pid = NULL;
+       vcpu->pv_unhalted = 0;
        init_waitqueue_head(&vcpu->wq);
        kvm_async_pf_vcpu_init(vcpu);
 
@@ -1567,6 +1568,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
                prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
 
                if (kvm_arch_vcpu_runnable(vcpu)) {
+                       vcpu->pv_unhalted = 0;
+                       /* preventing reordering should be enough here */
+                       barrier();
                        kvm_make_request(KVM_REQ_UNHALT, vcpu);
                        break;
                }


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