Re: [Xen-devel] [PATCH v2 6/6] xen/arm: update the docs about heterogeneous computing

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 20 Feb 2018, Julien Grall wrote:
> Hi Stefano,
> 
> On 19/02/18 21:58, Stefano Stabellini wrote:
> > diff --git a/docs/misc/xen-command-line.markdown
> > b/docs/misc/xen-command-line.markdown
> > index 2184cb9..8997904 100644
> > --- a/docs/misc/xen-command-line.markdown
> > +++ b/docs/misc/xen-command-line.markdown
> > @@ -1007,7 +1007,12 @@ Control Xens use of the APEI Hardware Error Source
> > Table, should one be found.
> >     Say yes at your own risk if you want to enable heterogenous computing
> >   (such as big.LITTLE). This may result to an unstable and insecure
> > -platform. When the option is disabled (default), CPUs that are not
> > +platform, unless you manually specify the cpu affinity of all domains so
> > +that all vcpus are scheduled on the same class of pcpus (big or LITTLE
> > +but not both). vcpu migration between big cores and LITTLE cores is not
> > +supported. See docs/misc/arm/big.LITTLE.txt for more information.
> > +
> > +When the hmp-unsafe option is disabled (default), CPUs that are not
> >   identical to the boot CPU will be parked and not used by Xen.
> >     ### hpetbroadcast
> > diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> > index 122c0b5..d04b7c7 100644
> > --- a/xen/arch/arm/smpboot.c
> > +++ b/xen/arch/arm/smpboot.c
> > @@ -266,7 +266,7 @@ void __init smp_init_cpus(void)
> >         if ( opt_hmp_unsafe )
> >           warning_add("WARNING: HMP COMPUTING HAS BEEN ENABLED.\n"
> > -                    "It has implications on the security and stability of
> > the system.\n");
> > +                    "It has implications on the security and stability of
> > the system, unless the cpu affinity of all domains is specified.\n");
> 
> The warning message will not be print nicely on serial. Please make sure it is
> split at 72 characters.

OK


> >   }
> >     int __init
> > @@ -308,13 +308,14 @@ void start_secondary(unsigned long boot_phys_offset,
> >       /*
> >        * Currently Xen assumes the platform has only one kind of CPUs.
> >        * This assumption does not hold on big.LITTLE platform and may
> > -     * result to instability and insecure platform. Better to park them
> > -     * for now.
> > +     * result to instability and insecure platform (unless cpu affinity
> > +     * is manually specified for all domains). Better to park them for
> > +     * now.
> >        */
> >       if ( !opt_hmp_unsafe &&
> >            current_cpu_data.midr.bits != boot_cpu_data.midr.bits )
> >       {
> > -        printk(XENLOG_ERR "CPU%u MIDR (0x%x) does not match boot CPU MIDR
> > (0x%x).\n",
> > +        printk(XENLOG_ERR "CPU%u MIDR (0x%x) does not match boot CPU MIDR
> > (0x%x), disable cpu (see big.LITTLE.txt under docs/).\n",
> 
> Same here.
> 
> >                  smp_processor_id(), current_cpu_data.midr.bits,
> >                  boot_cpu_data.midr.bits);
> >           stop_cpu();
> > 
> 
> Cheers,
> 
> -- 
> Julien Grall
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel