Re: [PATCH] zcrypt: handle AP Info notification from CHSC SEI command

From: Tony Krowiak <akrowiak@linux.ibm.com>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Sebastian Ott <sebott@linux.ibm.com>,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	oberpar@linux.ibm.com, freude@linux.ibm.com,
	pmorel@linux.ibm.com, pasic@linux.ibm.com, cohuck@redhat.com
Subject: Re: [PATCH] zcrypt: handle AP Info notification from CHSC SEI command
Date: Fri, 1 Feb 2019 10:38:32 -0500	[thread overview]
Message-ID: <a02f611b-370c-85b3-9e3d-c7dc2462004d@linux.ibm.com> (raw)
In-Reply-To: <20190201090159.GC3770@osiris>

On 2/1/19 4:01 AM, Heiko Carstens wrote:
> On Thu, Jan 31, 2019 at 06:28:39PM -0500, Tony Krowiak wrote:
>> On 1/30/19 1:32 PM, Sebastian Ott wrote:
>>> On Wed, 30 Jan 2019, Tony Krowiak wrote:
>>>> +#if IS_ENABLED(CONFIG_ZCRYPT)
>>>> +void ap_bus_cfg_chg(void);
>>>> +#else
>>>> +#error "no CONFIG_ZCRYPT"
>>>     ^
>>> I don't think that's the right thing to do here.
>>
>> I'd like to leave it. If somebody edits .config
>> and sets CONFIG_ZCRYPT=n, then the build will
>> fail. The preprocessor error above tells them
>> why.
> 
> No, the kernel build should never fail if a config option is not set.
> Also the above should be "#ifdef CONFIG_ZCRYPT".

Will do.

> 
> In addition (this isn't quoted unfortunately) the alternative function
> in the header file is missing the "inline" attribute. Can you please
> add that too?

I can.

> 
> static inline void ap_bus_cfg_chg(void) { }
> 
>>>> +* A config change has happened, Force an ap bus rescan.
>>>> +*/
>>>> +void ap_bus_cfg_chg(void)
>>>> +{
>>>> +	AP_DBF(DBF_INFO, "%s config change, forcing bus rescan\n", __func__);
>>>> +
>>>> +	ap_bus_force_rescan();
>>>> +}
>>>> +EXPORT_SYMBOL(ap_bus_cfg_chg);
>>>
>>> There is no need for the export symbol - you don't call that function
>> >from module code.
>>> As an unrelated question, just to be sure: ap_bus.c is compiled as
>>> built-in even with ZCRYPT=m, right?
>>
>> No. If you edit .config and set CONFIG_ZCRYPT=m, ap_bus.c will be built
>> into the zcrypt.ko module. Through some other magic, the zcrypt module
>> is loaded when linux boots.
> 
> If that happens, then we have a build problem that needs to be
> fixed. What exactly are you doing to get the ap code linked into the
> zcrypt module?

To tell you the truth, I don't know. The build configuration precedes my
creating this patch by many years. I only discovered these anomalies by
playing with the CONFIG_ZCRYPT option in response to Sebastian's
comments. I will have to take this up with our internal IBM maintainer.

> 