[Xen-devel] Question on hvc console init

[Iurii Konovalenko <iurii.konovalenko@xxxxxxxxxxxxxxx>]

Hello, all!

I try to bring up Xen on Renesas Lager board (r8a7790 SoC - R-Car H2).
Xen revision is 4.4.
I try to run Linux (kernel 3.14 + LTSI patches) as Dom0.
In kernel I've found strange behaviour in hvc console init function.
In file drivers/tty/hvc/hvc_xen.c in function xen_cons_init(void) sources are:

    if (!xen_domain())
        return 0;

    if (xen_initial_domain())
        ops = &dom0_hvc_ops;
    else {

xen_domain() and xen_initial_domain() are defined to check
xen_domain_type variable. This variable is defined and initialized to
XEN_NATIVE in arch/arm/xen/enlighten.c. The real value of this
variable is set in same file function xen_guest_init(), that is
early_initcall. But eraly_initcall is called later, than
console_initcall, that's why in time of running xen_cons_init(void)
xen_domain_type is not initialized to correct value and
xen_cons_init() does not initialize console, as returns on first check
"if (!xen_domain())".
It is not critical in normal operation, because we have
device_initcall xen_hvc_init() that is called after xen_guest_init(),
it initialize hvc. But in case of kernel falls before
device_initcall's, we can't see any printouts, that could be useful.

Could you please explain, may be using some configs or arguments in
command line for kernel, how to enable this early console?

Best regards.

Iurii Konovalenko | Senior Software Engineer
GlobalLogic

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