linux-kernel - Re: [PATCH 07/15] x86/split_lock: Handle suspend/hibernate and resume

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Date:   Mon, 14 May 2018 23:42:44 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        Alan Cox <alan@...ux.intel.com>, x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/15] x86/split_lock: Handle suspend/hibernate and resume

On Monday, May 14, 2018 8:52:17 PM CEST Fenghua Yu wrote:
> During suspend or hibernation, system enters BIOS. To avoid potential
> BIOS issue that may generate #AC exception for split locked accesses,
> handle the #AC as fatal exception, and block suspend or hibernation,
> the split lock setting is restored to BIOS setting. When resuming
> from suspend or hibernation, the split lock setting is restored to
> kernel setting.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  arch/x86/include/asm/cpu.h       |  2 ++
>  arch/x86/kernel/cpu/split_lock.c | 54 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
> index 0b00033b6fa8..89d62d7051fa 100644
> --- a/arch/x86/include/asm/cpu.h
> +++ b/arch/x86/include/asm/cpu.h
> @@ -45,11 +45,13 @@ int __init enumerate_split_lock(void);
>  void setup_split_lock(void);
>  bool do_split_lock_exception(struct pt_regs *regs, unsigned long error_code);
>  bool restore_split_lock_ac_bios(int *enable);
> +bool restore_split_lock_ac_kernel(int *enable);
>  #else /* CONFIG_SPLIT_LOCK_AC */
>  static inline int enumerate_split_lock(void) { return 0; }
>  static inline void setup_split_lock(void) {}
>  static inline bool
>  do_split_lock_exception(struct pt_regs *regs, unsigned long error_code) {}
>  static inline bool restore_split_lock_ac_bios(int *enable) { return true; }
> +static inline bool restore_split_lock_ac_kernel(int *enable) { return true; }
>  #endif /* CONFIG_SPLIT_LOCK_AC */
>  #endif /* _ASM_X86_CPU_H */
> diff --git a/arch/x86/kernel/cpu/split_lock.c b/arch/x86/kernel/cpu/split_lock.c
> index d2735259800b..5187a9c6cea6 100644
> --- a/arch/x86/kernel/cpu/split_lock.c
> +++ b/arch/x86/kernel/cpu/split_lock.c
> @@ -14,6 +14,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/cpu.h>
>  #include <linux/reboot.h>
> +#include <linux/syscore_ops.h>
>  #include <asm/msr.h>
>  
>  static bool split_lock_ac_supported;
> @@ -143,6 +144,15 @@ bool restore_split_lock_ac_bios(int *enable)
>  	return restore_split_lock_ac(split_lock_ac_bios);
>  }
>  
> +/* Restore kernel setting for #AC enable bit for split lock. */
> +bool restore_split_lock_ac_kernel(int *enable)
> +{
> +	if (enable)
> +		*enable = split_lock_ac == ENABLE_SPLIT_LOCK_AC ?  1 : 0;
> +
> +	return restore_split_lock_ac(split_lock_ac);
> +}
> +
>  static void split_lock_cpu_reboot(void *unused)
>  {
>  	restore_split_lock_ac_bios(NULL);
> @@ -223,11 +233,55 @@ bool do_split_lock_exception(struct pt_regs *regs, unsigned long error_code)
>  	return true;
>  }
>  
> +static int split_lock_offline(unsigned int cpu)
> +{
> +	int enable;
> +
> +	if (restore_split_lock_ac_bios(&enable))
> +		pr_info("%s split lock on CPU%d\n",
> +			enable ? "enable" : "disable", smp_processor_id());
> +
> +	return 0;
> +}
> +
> +static int split_lock_bsp_suspend(void)
> +{
> +	restore_split_lock_ac_bios(NULL);
> +
> +	return 0;
> +}
> +
> +static void split_lock_bsp_resume(void)
> +{
> +	restore_split_lock_ac_kernel(NULL);
> +}
> +
> +static struct syscore_ops split_lock_syscore_ops = {
> +	.suspend	= split_lock_bsp_suspend,
> +	.resume		= split_lock_bsp_resume,
> +};
> +
>  static int __init split_lock_init(void)
>  {
> +	int ret;
> +
> +	if (!split_lock_ac_supported)
> +		return -ENODEV;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
> +				"x86/split_lock:online:",
> +				NULL, split_lock_offline);
> +	if (ret < 0)
> +		goto out_fail;
> +
> +	register_syscore_ops(&split_lock_syscore_ops);
> +
>  	register_reboot_notifier(&split_lock_reboot_nb);
>  
>  	return 0;
> +
> +out_fail:
> +	return ret;
>  }
>  
>  late_initcall(split_lock_init);
>