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2024-05-14 bedbef8ad3e75a304af6361af235302bcc61d06b 
 kernel/arch/arm64/kernel/paravirt.c
....@@ -1,25 +1,175 @@
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+// SPDX-License-Identifier: GPL-2.0-only
12 /*
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- * This program is free software; you can redistribute it and/or modify
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- * it under the terms of the GNU General Public License version 2 as
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- * published by the Free Software Foundation.
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- *
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- * This program is distributed in the hope that it will be useful,
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- * but WITHOUT ANY WARRANTY; without even the implied warranty of
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- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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- * GNU General Public License for more details.
103  *
114  * Copyright (C) 2013 Citrix Systems
125  *
136  * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
147  */
158 
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+#define pr_fmt(fmt) "arm-pv: " fmt
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+
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+#include <linux/arm-smccc.h>
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+#include <linux/cpuhotplug.h>
1613 #include <linux/export.h>
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+#include <linux/io.h>
1715 #include <linux/jump_label.h>
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+#include <linux/printk.h>
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+#include <linux/psci.h>
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+#include <linux/reboot.h>
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+#include <linux/slab.h>
1820 #include <linux/types.h>
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+
1922 #include <asm/paravirt.h>
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+#include <asm/pvclock-abi.h>
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+#include <asm/smp_plat.h>
2025 
2126 struct static_key paravirt_steal_enabled;
2227 struct static_key paravirt_steal_rq_enabled;
2328 
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-struct pv_time_ops pv_time_ops;
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-EXPORT_SYMBOL_GPL(pv_time_ops);
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+struct paravirt_patch_template pv_ops;
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+EXPORT_SYMBOL_GPL(pv_ops);
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+
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+struct pv_time_stolen_time_region {
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+	struct pvclock_vcpu_stolen_time __rcu *kaddr;
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+};
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+
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+static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
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+
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+static bool steal_acc = true;
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+static int __init parse_no_stealacc(char *arg)
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+{
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+	steal_acc = false;
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+	return 0;
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+}
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+
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+early_param("no-steal-acc", parse_no_stealacc);
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+
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+/* return stolen time in ns by asking the hypervisor */
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+static u64 pv_steal_clock(int cpu)
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+{
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+	struct pvclock_vcpu_stolen_time *kaddr = NULL;
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+	struct pv_time_stolen_time_region *reg;
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+	u64 ret = 0;
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+
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+	reg = per_cpu_ptr(&stolen_time_region, cpu);
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+
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+	/*
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+	 * paravirt_steal_clock() may be called before the CPU
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+	 * online notification callback runs. Until the callback
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+	 * has run we just return zero.
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+	 */
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+	rcu_read_lock();
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+	kaddr = rcu_dereference(reg->kaddr);
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+	if (!kaddr) {
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+		rcu_read_unlock();
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+		return 0;
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+	}
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+
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+	ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time));
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+	rcu_read_unlock();
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+	return ret;
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+}
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+
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+static int stolen_time_cpu_down_prepare(unsigned int cpu)
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+{
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+	struct pvclock_vcpu_stolen_time *kaddr = NULL;
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+	struct pv_time_stolen_time_region *reg;
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+
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+	reg = this_cpu_ptr(&stolen_time_region);
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+	if (!reg->kaddr)
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+		return 0;
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+
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+	kaddr = rcu_replace_pointer(reg->kaddr, NULL, true);
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+	synchronize_rcu();
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+	memunmap(kaddr);
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+
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+	return 0;
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+}
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+
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+static int stolen_time_cpu_online(unsigned int cpu)
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+{
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+	struct pvclock_vcpu_stolen_time *kaddr = NULL;
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+	struct pv_time_stolen_time_region *reg;
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+	struct arm_smccc_res res;
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+
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+	reg = this_cpu_ptr(&stolen_time_region);
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+
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+	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
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+
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+	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
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+		return -EINVAL;
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+
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+	kaddr = memremap(res.a0,
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+			      sizeof(struct pvclock_vcpu_stolen_time),
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+			      MEMREMAP_WB);
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+
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+	rcu_assign_pointer(reg->kaddr, kaddr);
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+
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+	if (!reg->kaddr) {
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+		pr_warn("Failed to map stolen time data structure\n");
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+		return -ENOMEM;
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+	}
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+
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+	if (le32_to_cpu(kaddr->revision) != 0 ||
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+	    le32_to_cpu(kaddr->attributes) != 0) {
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+		pr_warn_once("Unexpected revision or attributes in stolen time data\n");
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+		return -ENXIO;
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+	}
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+
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+	return 0;
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+}
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+
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+static int __init pv_time_init_stolen_time(void)
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+{
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+	int ret;
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+
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+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
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+				"hypervisor/arm/pvtime:online",
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+				stolen_time_cpu_online,
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+				stolen_time_cpu_down_prepare);
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+	if (ret < 0)
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+		return ret;
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+	return 0;
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+}
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+
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+static bool __init has_pv_steal_clock(void)
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+{
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+	struct arm_smccc_res res;
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+
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+	/* To detect the presence of PV time support we require SMCCC 1.1+ */
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+	if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
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+		return false;
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+
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+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
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+			     ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
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+
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+	if (res.a0 != SMCCC_RET_SUCCESS)
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+		return false;
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+
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+	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
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+			     ARM_SMCCC_HV_PV_TIME_ST, &res);
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+
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+	return (res.a0 == SMCCC_RET_SUCCESS);
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+}
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+
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+int __init pv_time_init(void)
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+{
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+	int ret;
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+
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+	if (!has_pv_steal_clock())
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+		return 0;
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+
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+	ret = pv_time_init_stolen_time();
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+	if (ret)
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+		return ret;
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+
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+	pv_ops.time.steal_clock = pv_steal_clock;
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+
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+	static_key_slow_inc(&paravirt_steal_enabled);
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+	if (steal_acc)
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+		static_key_slow_inc(&paravirt_steal_rq_enabled);
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+
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+	pr_info("using stolen time PV\n");
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+
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+	return 0;
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+}