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

[Tony Krowiak]

On 2/4/19 5:06 AM, Harald Freudenberger wrote:
> On 01.02.19 16:38, Tony Krowiak wrote:
> > 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"
> > > > >  ÂÂÂ ^
> > > > > 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)
> > > > > > +{
> > > > > > +ÂÂÂ AP_DBF(DBF_INFO, "%s config change, forcing bus rescan\n", __func__);
> > > > > > +
> > > > > > +ÂÂÂ 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.
> >
> > >
> As Martin already pointed out the ap bus code is statically build into the kernel
> with this line in the Makefile:
>  Â obj-$(subst m,y,$(CONFIG_ZCRYPT)) += ap.o
> So CONFIG_ZCRYPT may have the value 'm' or 'y'
> and this is also the reason why a simple #ifdef CONFIG_ZCRYPT does not
> work, instead #if IS_ENABLED(CONFIG_ZCRYPT) has to be used.
>
> Only the ap stuff (which is: ap_bus.o, ap_card.o and ap_queue.o) is statically
> build into the kernel. The zcrypt kernel module is loaded as a dependency
> when a crypto card is detected. So detecting a CEX4 forces kernel module
> zcrypt_cex4.ko which forces the zcrypt.ko to insert into the kernel.
> So all global functions in ap_bus.c are available when CONFIG_ZCRYPT is
> enabled. However, I thought the symbol still needs an EXPORT_SYMBOL()
> statement. Otherwise I should throw out all these statements.
>
> Harald

Thank you for explaining that Harald.

Tony K

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