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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2023 Ventana Micro Systems Inc.
*/
#define pr_fmt(fmt) "riscv-pv: " fmt
#include <linux/cpuhotplug.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/jump_label.h>
#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/percpu-defs.h>
#include <linux/printk.h>
#include <linux/static_call.h>
#include <linux/types.h>
#include <asm/barrier.h>
#include <asm/page.h>
#include <asm/paravirt.h>
#include <asm/sbi.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);
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);
static DEFINE_PER_CPU(struct sbi_sta_struct, steal_time) __aligned(64);
static bool __init has_pv_steal_clock(void)
{
if (sbi_spec_version >= sbi_mk_version(2, 0) &&
sbi_probe_extension(SBI_EXT_STA) > 0) {
pr_info("SBI STA extension detected\n");
return true;
}
return false;
}
static int sbi_sta_steal_time_set_shmem(unsigned long lo, unsigned long hi,
unsigned long flags)
{
struct sbiret ret;
ret = sbi_ecall(SBI_EXT_STA, SBI_EXT_STA_STEAL_TIME_SET_SHMEM,
lo, hi, flags, 0, 0, 0);
if (ret.error) {
if (lo == SBI_SHMEM_DISABLE && hi == SBI_SHMEM_DISABLE)
pr_warn("Failed to disable steal-time shmem");
else
pr_warn("Failed to set steal-time shmem");
return sbi_err_map_linux_errno(ret.error);
}
return 0;
}
static int pv_time_cpu_online(unsigned int cpu)
{
struct sbi_sta_struct *st = this_cpu_ptr(&steal_time);
phys_addr_t pa = __pa(st);
unsigned long lo = (unsigned long)pa;
unsigned long hi = IS_ENABLED(CONFIG_32BIT) ? upper_32_bits((u64)pa) : 0;
return sbi_sta_steal_time_set_shmem(lo, hi, 0);
}
static int pv_time_cpu_down_prepare(unsigned int cpu)
{
return sbi_sta_steal_time_set_shmem(SBI_SHMEM_DISABLE,
SBI_SHMEM_DISABLE, 0);
}
static u64 pv_time_steal_clock(int cpu)
{
struct sbi_sta_struct *st = per_cpu_ptr(&steal_time, cpu);
__le32 sequence;
__le64 steal;
/*
* Check the sequence field before and after reading the steal
* field. Repeat the read if it is different or odd.
*/
do {
sequence = READ_ONCE(st->sequence);
virt_rmb();
steal = READ_ONCE(st->steal);
virt_rmb();
} while ((le32_to_cpu(sequence) & 1) ||
sequence != READ_ONCE(st->sequence));
return le64_to_cpu(steal);
}
int __init pv_time_init(void)
{
int ret;
if (!has_pv_steal_clock())
return 0;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
"riscv/pv_time:online",
pv_time_cpu_online,
pv_time_cpu_down_prepare);
if (ret < 0)
return ret;
static_call_update(pv_steal_clock, pv_time_steal_clock);
static_key_slow_inc(¶virt_steal_enabled);
if (steal_acc)
static_key_slow_inc(¶virt_steal_rq_enabled);
pr_info("Computing paravirt steal-time\n");
return 0;
}
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