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

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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"
     ^
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.



As Martin already pointed out the ap bus code is statically build into the kernel
with this line in the Makefile:
   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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