paravirt.c
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// 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 <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;
struct paravirt_patch_template pv_ops;
EXPORT_SYMBOL_GPL(pv_ops);
struct pv_time_stolen_time_region {
struct pvclock_vcpu_stolen_time *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 pv_steal_clock(int cpu)
{
struct pv_time_stolen_time_region *reg;
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.
*/
if (!reg->kaddr)
return 0;
return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
}
static int stolen_time_cpu_down_prepare(unsigned int cpu)
{
struct pv_time_stolen_time_region *reg;
reg = this_cpu_ptr(&stolen_time_region);
if (!reg->kaddr)
return 0;
memunmap(reg->kaddr);
memset(reg, 0, sizeof(*reg));
return 0;
}
static int stolen_time_cpu_online(unsigned int cpu)
{
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;
reg->kaddr = memremap(res.a0,
sizeof(struct pvclock_vcpu_stolen_time),
MEMREMAP_WB);
if (!reg->kaddr) {
pr_warn("Failed to map stolen time data structure\n");
return -ENOMEM;
}
if (le32_to_cpu(reg->kaddr->revision) != 0 ||
le32_to_cpu(reg->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;
pv_ops.time.steal_clock = pv_steal_clock;
static_key_slow_inc(¶virt_steal_enabled);
if (steal_acc)
static_key_slow_inc(¶virt_steal_rq_enabled);
pr_info("using stolen time PV\n");
return 0;
}