Re: Boot time and 3 sec in warning_print

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 15/02/2021 08:51, Jürgen Groß wrote:
> On 15.02.21 09:38, Jan Beulich wrote:
> > On 15.02.2021 09:13, Jürgen Groß wrote:
> > > On 15.02.21 08:37, Anders Törnqvist wrote:
> > > > I would like to shorten the boot time in our system if possible.
> > > >
> > > > In xen/common/warning.c there is warning_print() which contains a 3
> > > > seconds loop that calls  process_pending_softirqs().
> > > >
> > > > What would the potential problems be if that loop is radically 
> > > > shortened?
> > > A user might not notice the warning(s) printed.
> > >
> > > But I can see your point. I think adding a boot option for setting
> > > another timeout value (e.g. 0) would do the job without compromising
> > > the default case.
> > I don't think I agree - the solution to this is to eliminate the
> > reason leading to the warning. The delay is intentionally this way
> > to annoy the admin and force them to take measures.
> OTOH there are some warnings which can't be dealt with via boot
> parameters or which can be solved by other means, e.g
Both of the warning can be removed...

> "WARNING: SILO mode is not enabled.\n"
> "It has implications on the security of the system,\n"
> "unless the communications have been forbidden between\n"
> "untrusted domains.\n"
The default Arm config will use SILO mode. You would have needed to 
tweak your .config in order to get this message.
There are current discussion to allow again FLASK on Armv8.1+ platform 
(see [1]).
> "WARNING: HMP COMPUTING HAS BEEN ENABLED.\n"
> "It has implications on the security and stability of the system,\n"
> "unless the cpu affinity of all domains is specified.\n"
This is printed if the admin add "hmp-unsafe=yes" on the command line.

Cheers,

[1]
https://lore.kernel.org/xen-devel/20201111215203.80336-1-ash.j.wilding@xxxxxxxxx/

--
Julien Grall