Commit 323925ed authored by Andrew Jones's avatar Andrew Jones Committed by Anup Patel
Browse files

RISC-V: paravirt: Add skeleton for pv-time support 



Add the files and functions needed to support paravirt time on
RISC-V. Also include the common code needed for the first
application of pv-time, which is steal-time. In the next
patches we'll complete the functions to fully enable steal-time
support.

Acked-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Reviewed-by: default avatarAtish Patra <atishp@rivosinc.com>
Signed-off-by: default avatarAndrew Jones <ajones@ventanamicro.com>
Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent 4c460eb3

Documentation/admin-guide/kernel-parameters.txt

+3 −3
Original line number Diff line number Diff line
@@ -3985,9 +3985,9 @@ 
			vulnerability. System may allow data leaks with this

			option.



	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized

			steal time accounting. steal time is computed, but

			won't influence scheduler behaviour

	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES,RISCV] Disable

			paravirtualized steal time accounting. steal time is

			computed, but won't influence scheduler behaviour



	nosync		[HW,M68K] Disables sync negotiation for all devices.

arch/riscv/include/asm/paravirt.h

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+28 −0
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/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_RISCV_PARAVIRT_H

#define _ASM_RISCV_PARAVIRT_H



#ifdef CONFIG_PARAVIRT

#include <linux/static_call_types.h>



struct static_key;

extern struct static_key paravirt_steal_enabled;

extern struct static_key paravirt_steal_rq_enabled;



u64 dummy_steal_clock(int cpu);



DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);



static inline u64 paravirt_steal_clock(int cpu)

{

	return static_call(pv_steal_clock)(cpu);

}



int __init pv_time_init(void);



#else



#define pv_time_init() do {} while (0)



#endif /* CONFIG_PARAVIRT */

#endif /* _ASM_RISCV_PARAVIRT_H */

arch/riscv/include/asm/paravirt_api_clock.h

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#include <asm/paravirt.h>

arch/riscv/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ obj-$(CONFIG_SMP) += sbi-ipi.o 
obj-$(CONFIG_SMP) += cpu_ops_sbi.o

endif

obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o

obj-$(CONFIG_PARAVIRT)		+= paravirt.o

obj-$(CONFIG_KGDB)		+= kgdb.o

obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o

obj-$(CONFIG_KEXEC_FILE)	+= elf_kexec.o machine_kexec_file.o

arch/riscv/kernel/paravirt.c

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Original line number Diff line number Diff line 
// 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/init.h>

#include <linux/jump_label.h>

#include <linux/printk.h>

#include <linux/static_call.h>

#include <linux/types.h>



#include <asm/paravirt.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 bool __init has_pv_steal_clock(void)

{

	return false;

}



static int pv_time_cpu_online(unsigned int cpu)

{

	return 0;

}



static int pv_time_cpu_down_prepare(unsigned int cpu)

{

	return 0;

}



static u64 pv_time_steal_clock(int cpu)

{

	return 0;

}



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(&paravirt_steal_enabled);

	if (steal_acc)

		static_key_slow_inc(&paravirt_steal_rq_enabled);



	pr_info("Computing paravirt steal-time\n");



	return 0;

}