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linux-next/arch/arm64/kernel/paravirt.c
Steven Price e0685fa228 arm64: Retrieve stolen time as paravirtualized guest
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>
2019-10-21 19:20:31 +01:00

159 lines
3.3 KiB
C

// 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);
if (!reg->kaddr) {
pr_warn_once("stolen time enabled but not configured for cpu %d\n",
cpu);
return 0;
}
return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
}
static int stolen_time_dying_cpu(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 init_stolen_time_cpu(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 pv_time_init_stolen_time(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
"hypervisor/arm/pvtime:starting",
init_stolen_time_cpu, stolen_time_dying_cpu);
if (ret < 0)
return ret;
return 0;
}
static bool has_pv_steal_clock(void)
{
struct arm_smccc_res res;
/* To detect the presence of PV time support we require SMCCC 1.1+ */
if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
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(&paravirt_steal_enabled);
if (steal_acc)
static_key_slow_inc(&paravirt_steal_rq_enabled);
pr_info("using stolen time PV\n");
return 0;
}