summaryrefslogtreecommitdiffstats
path: root/arch/arm64/kernel/paravirt.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/arm64/kernel/paravirt.c')
-rw-r--r--arch/arm64/kernel/paravirt.c180
1 files changed, 180 insertions, 0 deletions
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
new file mode 100644
index 000000000..57c7c211f
--- /dev/null
+++ b/arch/arm64/kernel/paravirt.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2013 Citrix Systems
+ *
+ * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
+ */
+
+#define pr_fmt(fmt) "arm-pv: " fmt
+
+#include <linux/arm-smccc.h>
+#include <linux/cpuhotplug.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/jump_label.h>
+#include <linux/printk.h>
+#include <linux/psci.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/static_call.h>
+
+#include <asm/paravirt.h>
+#include <asm/pvclock-abi.h>
+#include <asm/smp_plat.h>
+
+struct static_key paravirt_steal_enabled;
+struct static_key paravirt_steal_rq_enabled;
+
+static u64 native_steal_clock(int cpu)
+{
+ return 0;
+}
+
+DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
+
+struct pv_time_stolen_time_region {
+ struct pvclock_vcpu_stolen_time __rcu *kaddr;
+};
+
+static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
+
+static bool steal_acc = true;
+static int __init parse_no_stealacc(char *arg)
+{
+ steal_acc = false;
+ return 0;
+}
+
+early_param("no-steal-acc", parse_no_stealacc);
+
+/* return stolen time in ns by asking the hypervisor */
+static u64 para_steal_clock(int cpu)
+{
+ struct pvclock_vcpu_stolen_time *kaddr = NULL;
+ struct pv_time_stolen_time_region *reg;
+ u64 ret = 0;
+
+ reg = per_cpu_ptr(&stolen_time_region, cpu);
+
+ /*
+ * paravirt_steal_clock() may be called before the CPU
+ * online notification callback runs. Until the callback
+ * has run we just return zero.
+ */
+ rcu_read_lock();
+ kaddr = rcu_dereference(reg->kaddr);
+ if (!kaddr) {
+ rcu_read_unlock();
+ return 0;
+ }
+
+ ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time));
+ rcu_read_unlock();
+ return ret;
+}
+
+static int stolen_time_cpu_down_prepare(unsigned int cpu)
+{
+ struct pvclock_vcpu_stolen_time *kaddr = NULL;
+ struct pv_time_stolen_time_region *reg;
+
+ reg = this_cpu_ptr(&stolen_time_region);
+ if (!reg->kaddr)
+ return 0;
+
+ kaddr = rcu_replace_pointer(reg->kaddr, NULL, true);
+ synchronize_rcu();
+ memunmap(kaddr);
+
+ return 0;
+}
+
+static int stolen_time_cpu_online(unsigned int cpu)
+{
+ struct pvclock_vcpu_stolen_time *kaddr = NULL;
+ struct pv_time_stolen_time_region *reg;
+ struct arm_smccc_res res;
+
+ reg = this_cpu_ptr(&stolen_time_region);
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+ if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+ return -EINVAL;
+
+ kaddr = memremap(res.a0,
+ sizeof(struct pvclock_vcpu_stolen_time),
+ MEMREMAP_WB);
+
+ rcu_assign_pointer(reg->kaddr, kaddr);
+
+ if (!reg->kaddr) {
+ pr_warn("Failed to map stolen time data structure\n");
+ return -ENOMEM;
+ }
+
+ if (le32_to_cpu(kaddr->revision) != 0 ||
+ le32_to_cpu(kaddr->attributes) != 0) {
+ pr_warn_once("Unexpected revision or attributes in stolen time data\n");
+ return -ENXIO;
+ }
+
+ return 0;
+}
+
+static int __init pv_time_init_stolen_time(void)
+{
+ int ret;
+
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+ "hypervisor/arm/pvtime:online",
+ stolen_time_cpu_online,
+ stolen_time_cpu_down_prepare);
+ if (ret < 0)
+ return ret;
+ return 0;
+}
+
+static bool __init has_pv_steal_clock(void)
+{
+ struct arm_smccc_res res;
+
+ /* To detect the presence of PV time support we require SMCCC 1.1+ */
+ if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
+ return false;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
+
+ if (res.a0 != SMCCC_RET_SUCCESS)
+ return false;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
+ ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+ return (res.a0 == SMCCC_RET_SUCCESS);
+}
+
+int __init pv_time_init(void)
+{
+ int ret;
+
+ if (!has_pv_steal_clock())
+ return 0;
+
+ ret = pv_time_init_stolen_time();
+ if (ret)
+ return ret;
+
+ static_call_update(pv_steal_clock, para_steal_clock);
+
+ static_key_slow_inc(&paravirt_steal_enabled);
+ if (steal_acc)
+ static_key_slow_inc(&paravirt_steal_rq_enabled);
+
+ pr_info("using stolen time PV\n");
+
+ return 0;
+}