On Thu, Mar 17, 2016 at 09:08:09PM +0000, Qais Yousef wrote: > Malta defconfig compiles with GIC on. Hence when compiling for SMP it causes the > new IPI code to be activated. But on qemu malta there's no GIC causing a > BUG_ON(!ipidomain) to be hit in mips_smp_ipi_init(). > > Since in that configuration one can only run a single core SMP (!), skip IPI > initialisation if we detect that this is the case. It is a sensible behaviour > to introduce and should keep such possible configuration to run rather than die > hard unnecessarily. > > Signed-off-by: Qais Yousef <qsyousef@xxxxxxxxx> > Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx> Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> > Cc: Guenter Roeck <linux@xxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: linux-mips@xxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > --- > arch/mips/kernel/smp.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c > index 37708d9..27cb638 100644 > --- a/arch/mips/kernel/smp.c > +++ b/arch/mips/kernel/smp.c > @@ -243,6 +243,18 @@ static int __init mips_smp_ipi_init(void) > struct irq_domain *ipidomain; > struct device_node *node; > > + /* > + * In some cases like qemu-malta, it is desired to try SMP with > + * a single core. Qemu-malta has no GIC, so an attempt to set any IPIs > + * would cause a BUG_ON() to be triggered since there's no ipidomain. > + * > + * Since for a single core system IPIs aren't required really, skip the > + * initialisation which should generally keep any such configurations > + * happy and only fail hard when trying to truely run SMP. > + */ > + if (cpumask_weight(cpu_possible_mask) == 1) > + return 0; > + > node = of_irq_find_parent(of_root); > ipidomain = irq_find_matching_host(node, DOMAIN_BUS_IPI); > > -- > 2.7.3 >
