[PATCH v3 8/8] KVM: arm64: Support the vCPU preemption check

@@ -29,6 +29,8 @@ static inline u64 paravirt_steal_clock(int cpu)
 
 int __init pv_time_init(void);
 
+int __init pv_lock_init(void);
+
 __visible bool __native_vcpu_is_preempted(int cpu);
 
 static inline bool pv_vcpu_is_preempted(int cpu)

@@ -39,6 +41,7 @@ static inline bool pv_vcpu_is_preempted(int cpu)
 #else
 
 #define pv_time_init() do {} while (0)
+#define pv_lock_init() do {} while (0)
 
 #endif // CONFIG_PARAVIRT
 

@@ -22,6 +22,8 @@
 #include <asm/paravirt.h>
 #include <asm/pvclock-abi.h>
 #include <asm/smp_plat.h>
+#include <asm/pvlock-abi.h>
+#include <asm/hypervisor.h>
 
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;

@@ -35,6 +37,10 @@ struct pv_time_stolen_time_region {
 	struct pvclock_vcpu_stolen_time *kaddr;
 };
 
+struct pv_lock_state_region {
+	struct pvlock_vcpu_state *kaddr;
+};
+
 static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
 
 static bool steal_acc = true;

@@ -158,3 +164,122 @@ int __init pv_time_init(void)
 
 	return 0;
 }
+
+static DEFINE_PER_CPU(struct pv_lock_state_region, lock_state_region);
+
+static bool kvm_vcpu_is_preempted(int cpu)
+{
+	struct pv_lock_state_region *reg;
+	__le64 preempted_le;
+
+	reg = per_cpu_ptr(&lock_state_region, cpu);
+	if (!reg->kaddr) {
+		pr_warn_once("PV lock enabled but not configured for cpu %d\n",
+			     cpu);
+		return false;
+	}
+
+	preempted_le = le64_to_cpu(READ_ONCE(reg->kaddr->preempted));
+
+	return !!preempted_le;
+}
+
+static int pvlock_vcpu_state_dying_cpu(unsigned int cpu)
+{
+	struct pv_lock_state_region *reg;
+
+	reg = this_cpu_ptr(&lock_state_region);
+	if (!reg->kaddr)
+		return 0;
+
+	memunmap(reg->kaddr);
+	memset(reg, 0, sizeof(*reg));
+
+	return 0;
+}
+
+static int init_pvlock_vcpu_state(unsigned int cpu)
+{
+	struct pv_lock_state_region *reg;
+	struct arm_smccc_res res;
+
+	reg = this_cpu_ptr(&lock_state_region);
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PV_LOCK_FUNC_ID,
+			     KVM_PV_LOCK_PREEMPTED, &res);
+
+	if (res.a0 == SMCCC_RET_NOT_SUPPORTED) {
+		pr_warn("Failed to init PV lock data structure\n");
+		return -EINVAL;
+	}
+
+	reg->kaddr = memremap(res.a0,
+			      sizeof(struct pvlock_vcpu_state),
+			      MEMREMAP_WB);
+
+	if (!reg->kaddr) {
+		pr_warn("Failed to map PV lock data structure\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int kvm_arm_init_pvlock(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ARM_KVM_PVLOCK_STARTING,
+				"hypervisor/arm/pvlock:starting",
+				init_pvlock_vcpu_state,
+				pvlock_vcpu_state_dying_cpu);
+	if (ret < 0) {
+		pr_warn("PV lock init failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static bool has_kvm_pvlock(void)
+{
+	struct arm_smccc_res res;
+
+	/* To detect the presence of PV lock support we require SMCCC 1.1+ */
+	if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
+		return false;
+
+	if (!kvm_arm_hyp_service_available(
+			ARM_SMCCC_VENDOR_HYP_KVM_PV_LOCK_FUNC_ID)) {
+		pr_warn("PV lock is not available\n");
+		return false;
+	}
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PV_LOCK_FUNC_ID,
+			     KVM_PV_LOCK_FEATURES, &res);
+
+	if (res.a0 != SMCCC_RET_SUCCESS)
+		return false;
+
+	return true;
+}
+
+int __init pv_lock_init(void)
+{
+	int ret;
+
+	if (is_hyp_mode_available())
+		return 0;
+
+	if (!has_kvm_pvlock())
+		return 0;
+
+	ret = kvm_arm_init_pvlock();
+	if (ret)
+		return ret;
+
+	pv_ops.lock.vcpu_is_preempted = kvm_vcpu_is_preempted;
+	pr_info("using PV lock preempted\n");
+
+	return 0;
+}

@@ -376,6 +376,8 @@ void __init setup_arch(char **cmdline_p)
 	smp_init_cpus();
 	smp_build_mpidr_hash();
 
+	pv_lock_init();
+
 	/* Init percpu seeds for random tags after cpus are set up. */
 	kasan_init_tags();
 

@@ -138,6 +138,7 @@ enum cpuhp_state {
 	CPUHP_AP_DUMMY_TIMER_STARTING,
 	CPUHP_AP_ARM_XEN_STARTING,
 	CPUHP_AP_ARM_KVMPV_STARTING,
+	CPUHP_AP_ARM_KVM_PVLOCK_STARTING,
 	CPUHP_AP_ARM_CORESIGHT_STARTING,
 	CPUHP_AP_ARM64_ISNDEP_STARTING,
 	CPUHP_AP_SMPCFD_DYING,