Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <1e1451c1-686c-d34a-4388-edb429c212a4@roeck-us.net>
Date:   Fri, 3 Feb 2023 10:34:49 -0800
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To:     Alexander Egorenkov <egorenar@linux.ibm.com>,
        wim@linux-watchdog.org
Cc:     linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org,
        hca@linux.ibm.com
References: <20230203073958.1585738-1-egorenar@linux.ibm.com>
 <20230203073958.1585738-4-egorenar@linux.ibm.com>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH 3/5] watchdog: diag288_wdt: unify command buffer handling
 for diag288 zvm
In-Reply-To: <20230203073958.1585738-4-egorenar@linux.ibm.com>
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On 2/2/23 23:39, Alexander Egorenkov wrote:
> Simplify and de-duplicate code by introducing a common single command
> buffer allocated once at initialization. Moreover, simplify the interface
> of __diag288_vm() by accepting ASCII strings as the command parameter
> and converting it to the EBCDIC format within the function itself.
> 
> Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
> Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
> ---
>   drivers/watchdog/diag288_wdt.c | 55 +++++++++++++---------------------
>   1 file changed, 20 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/watchdog/diag288_wdt.c b/drivers/watchdog/diag288_wdt.c
> index c8d516ced6d2..c717f47dd4c3 100644
> --- a/drivers/watchdog/diag288_wdt.c
> +++ b/drivers/watchdog/diag288_wdt.c
> @@ -69,6 +69,8 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default = C
>   
>   MODULE_ALIAS("vmwatchdog");
>   
> +static char *cmd_buf;
> +

Personally I wound not even bother allocating this, but that is just my personal
opinion. And I guess one more static variable doesn't make much of a difference
either.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

>   static int __diag288(unsigned int func, unsigned int timeout,
>   		     unsigned long action, unsigned int len)
>   {
> @@ -88,11 +90,18 @@ static int __diag288(unsigned int func, unsigned int timeout,
>   	return err;
>   }
>   
> -static int __diag288_vm(unsigned int  func, unsigned int timeout,
> -			char *cmd, size_t len)
> +static int __diag288_vm(unsigned int  func, unsigned int timeout, char *cmd)
>   {
> +	ssize_t len;
> +
> +	len = strscpy(cmd_buf, cmd, MAX_CMDLEN);
> +	if (len < 0)
> +		return len;
> +	ASCEBC(cmd_buf, MAX_CMDLEN);
> +	EBC_TOUPPER(cmd_buf, MAX_CMDLEN);
> +
>   	diag_stat_inc(DIAG_STAT_X288);
> -	return __diag288(func, timeout, virt_to_phys(cmd), len);
> +	return __diag288(func, timeout, virt_to_phys(cmd_buf), len);
>   }
>   
>   static int __diag288_lpar(unsigned int func, unsigned int timeout,
> @@ -104,24 +113,14 @@ static int __diag288_lpar(unsigned int func, unsigned int timeout,
>   
>   static int wdt_start(struct watchdog_device *dev)
>   {
> -	char *ebc_cmd;
> -	size_t len;
>   	int ret;
>   	unsigned int func;
>   
>   	if (MACHINE_IS_VM) {
> -		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
> -		if (!ebc_cmd)
> -			return -ENOMEM;
> -		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
> -		ASCEBC(ebc_cmd, MAX_CMDLEN);
> -		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
> -
>   		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
>   			: WDT_FUNC_INIT;
> -		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
> +		ret = __diag288_vm(func, dev->timeout, wdt_cmd);
>   		WARN_ON(ret != 0);
> -		kfree(ebc_cmd);
>   	} else {
>   		ret = __diag288_lpar(WDT_FUNC_INIT,
>   				     dev->timeout, LPARWDT_RESTART);
> @@ -146,19 +145,10 @@ static int wdt_stop(struct watchdog_device *dev)
>   
>   static int wdt_ping(struct watchdog_device *dev)
>   {
> -	char *ebc_cmd;
> -	size_t len;
>   	int ret;
>   	unsigned int func;
>   
>   	if (MACHINE_IS_VM) {
> -		ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
> -		if (!ebc_cmd)
> -			return -ENOMEM;
> -		len = strlcpy(ebc_cmd, wdt_cmd, MAX_CMDLEN);
> -		ASCEBC(ebc_cmd, MAX_CMDLEN);
> -		EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
> -
>   		/*
>   		 * It seems to be ok to z/VM to use the init function to
>   		 * retrigger the watchdog. On LPAR WDT_FUNC_CHANGE must
> @@ -167,9 +157,8 @@ static int wdt_ping(struct watchdog_device *dev)
>   		func = conceal_on ? (WDT_FUNC_INIT | WDT_FUNC_CONCEAL)
>   			: WDT_FUNC_INIT;
>   
> -		ret = __diag288_vm(func, dev->timeout, ebc_cmd, len);
> +		ret = __diag288_vm(func, dev->timeout, wdt_cmd);
>   		WARN_ON(ret != 0);
> -		kfree(ebc_cmd);
>   	} else {
>   		ret = __diag288_lpar(WDT_FUNC_CHANGE, dev->timeout, 0);
>   	}
> @@ -212,25 +201,20 @@ static struct watchdog_device wdt_dev = {
>   static int __init diag288_init(void)
>   {
>   	int ret;
> -	char ebc_begin[] = {
> -		194, 197, 199, 201, 213
> -	};
> -	char *ebc_cmd;
>   
>   	watchdog_set_nowayout(&wdt_dev, nowayout_info);
>   
>   	if (MACHINE_IS_VM) {
> -		ebc_cmd = kmalloc(sizeof(ebc_begin), GFP_KERNEL);
> -		if (!ebc_cmd) {
> +		cmd_buf = kmalloc(MAX_CMDLEN, GFP_KERNEL);
> +		if (!cmd_buf) {
>   			pr_err("The watchdog cannot be initialized\n");
>   			return -ENOMEM;
>   		}
> -		memcpy(ebc_cmd, ebc_begin, sizeof(ebc_begin));
> -		ret = __diag288_vm(WDT_FUNC_INIT, 15,
> -				   ebc_cmd, sizeof(ebc_begin));
> -		kfree(ebc_cmd);
> +
> +		ret = __diag288_vm(WDT_FUNC_INIT, MIN_INTERVAL, "BEGIN");
>   		if (ret != 0) {
>   			pr_err("The watchdog cannot be initialized\n");
> +			kfree(cmd_buf);
>   			return -EINVAL;
>   		}
>   	} else {
> @@ -251,6 +235,7 @@ static int __init diag288_init(void)
>   static void __exit diag288_exit(void)
>   {
>   	watchdog_unregister_device(&wdt_dev);
> +	kfree(cmd_buf);
>   }
>   
>   module_init(diag288_init);