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

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Message-Id: <20190201090159.GC3770@osiris>
Date:   Fri, 1 Feb 2019 10:01:59 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     Sebastian Ott <sebott@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, pmorel@...ux.ibm.com,
        pasic@...ux.ibm.com, cohuck@...hat.com
Subject: Re: [PATCH] zcrypt: handle AP Info notification from CHSC SEI command

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".

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?

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?