linux-kernel - Re: [RFC PATCH 4/4] watchdog: hpwdt: Make panic behaviour configurable

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Message-ID: <20190116023022.GE18342@anatevka>
Date:   Tue, 15 Jan 2019 19:30:22 -0700
From:   Jerry Hoemann <jerry.hoemann@....com>
To:     Ivan Mironov <mironov.ivan@...il.com>
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [RFC PATCH 4/4] watchdog: hpwdt: Make panic behaviour
 configurable

On Mon, Jan 14, 2019 at 07:36:17AM +0500, Ivan Mironov wrote:
> This adds an option to not panic on NMI even if it was caused by iLO.
> 
> Signed-off-by: Ivan Mironov <mironov.ivan@...il.com>
> ---
>  drivers/watchdog/hpwdt.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
> index 95d002b5b120..b12858491189 100644
> --- a/drivers/watchdog/hpwdt.c
> +++ b/drivers/watchdog/hpwdt.c
> @@ -37,6 +37,10 @@ static unsigned int soft_margin = DEFAULT_MARGIN;	/* in seconds */
>  static bool nowayout = WATCHDOG_NOWAYOUT;
>  static bool pretimeout = IS_ENABLED(CONFIG_HPWDT_NMI_DECODING);
>  
> +#ifdef CONFIG_HPWDT_NMI_DECODING
> +static bool panic_on_nmi = true;
> +#endif /* CONFIG_HPWDT_NMI_DECODING */
> +
>  static void __iomem *pci_mem_addr;		/* the PCI-memory address */
>  static unsigned long __iomem *hpwdt_nmistat;
>  static unsigned long __iomem *hpwdt_timer_reg;
> @@ -146,7 +150,10 @@ static int hpwdt_set_pretimeout(struct watchdog_device *wdd, unsigned int req)
>  
>  static int hpwdt_my_nmi(void)
>  {
> -	return ioread8(hpwdt_nmistat) & 0x6;
> +	int nmistat = ioread8(hpwdt_nmistat);
> +
> +	iowrite8(nmistat & ~0x6, hpwdt_nmistat);
> +	return nmistat & 0x6;


This is a read only register.


>  }
>  
>  /*
> @@ -168,7 +175,10 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
>  		 "4. iLO Event Log\n",
>  		 mynmi, ulReason, smp_processor_id());
>  
> -	nmi_panic(regs, "hpwdt: NMI: Not continuing");
> +	if (panic_on_nmi)
> +		nmi_panic(regs, "hpwdt: NMI: Not continuing");
> +
> +	pr_emerg("Dazed and confused, but trying to continue\n");
>  


The watchdog core provides a way to enable/disable the NMI pretimeout dynamically
via ioctl.  The pretimeout NMI can also be disabled via module parameter to hpwdt.
This adds complexity without really adding functionality.


BTW, don't reuse error messages.  Makes it difficult to tell where the error
originated from.


>  	return NMI_HANDLED;
>  }
> @@ -376,6 +386,9 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
>  #ifdef CONFIG_HPWDT_NMI_DECODING
>  module_param(pretimeout, bool, 0);
>  MODULE_PARM_DESC(pretimeout, "Watchdog pretimeout enabled");
> -#endif
> +
> +module_param(panic_on_nmi, bool, 0);
> +MODULE_PARM_DESC(panic_on_nmi, "Cause panic on NMI induced by iLO (default=1)");
> +#endif /* CONFIG_HPWDT_NMI_DECODING */
>  
>  module_pci_driver(hpwdt_driver);
> -- 
> 2.20.1

-- 

-----------------------------------------------------------------------------
Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
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