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e0685fa228
Enable paravirtualization features when running under a hypervisor supporting the PV_TIME_ST hypercall. For each (v)CPU, we ask the hypervisor for the location of a shared page which the hypervisor will use to report stolen time to us. We set pv_time_ops to the stolen time function which simply reads the stolen value from the shared page for a VCPU. We guarantee single-copy atomicity using READ_ONCE which means we can also read the stolen time for another VCPU than the currently running one while it is potentially being updated by the hypervisor. Signed-off-by: Steven Price <steven.price@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
159 lines
3.3 KiB
C
159 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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*
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* Copyright (C) 2013 Citrix Systems
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*
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* Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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*/
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#define pr_fmt(fmt) "arm-pv: " fmt
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#include <linux/arm-smccc.h>
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#include <linux/cpuhotplug.h>
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#include <linux/export.h>
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#include <linux/io.h>
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#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>
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#include <linux/types.h>
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#include <asm/paravirt.h>
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#include <asm/pvclock-abi.h>
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#include <asm/smp_plat.h>
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struct static_key paravirt_steal_enabled;
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struct static_key paravirt_steal_rq_enabled;
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struct paravirt_patch_template pv_ops;
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EXPORT_SYMBOL_GPL(pv_ops);
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struct pv_time_stolen_time_region {
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struct pvclock_vcpu_stolen_time *kaddr;
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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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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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early_param("no-steal-acc", parse_no_stealacc);
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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 pv_time_stolen_time_region *reg;
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reg = per_cpu_ptr(&stolen_time_region, cpu);
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if (!reg->kaddr) {
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pr_warn_once("stolen time enabled but not configured for cpu %d\n",
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cpu);
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return 0;
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}
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return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
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}
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static int stolen_time_dying_cpu(unsigned int cpu)
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{
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struct pv_time_stolen_time_region *reg;
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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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memunmap(reg->kaddr);
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memset(reg, 0, sizeof(*reg));
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return 0;
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}
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static int init_stolen_time_cpu(unsigned int cpu)
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{
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struct pv_time_stolen_time_region *reg;
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struct arm_smccc_res res;
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reg = this_cpu_ptr(&stolen_time_region);
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arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
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if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
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return -EINVAL;
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reg->kaddr = memremap(res.a0,
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sizeof(struct pvclock_vcpu_stolen_time),
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MEMREMAP_WB);
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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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if (le32_to_cpu(reg->kaddr->revision) != 0 ||
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le32_to_cpu(reg->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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return 0;
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}
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static int pv_time_init_stolen_time(void)
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{
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int ret;
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ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
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"hypervisor/arm/pvtime:starting",
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init_stolen_time_cpu, stolen_time_dying_cpu);
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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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static bool has_pv_steal_clock(void)
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{
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struct arm_smccc_res res;
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/* To detect the presence of PV time support we require SMCCC 1.1+ */
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if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
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return false;
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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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if (res.a0 != SMCCC_RET_SUCCESS)
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return false;
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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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return (res.a0 == SMCCC_RET_SUCCESS);
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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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if (!has_pv_steal_clock())
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return 0;
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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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pv_ops.time.steal_clock = pv_steal_clock;
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static_key_slow_inc(¶virt_steal_enabled);
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if (steal_acc)
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static_key_slow_inc(¶virt_steal_rq_enabled);
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pr_info("using stolen time PV\n");
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return 0;
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}
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