From 19fb5818ed60ac2e9609ad16bc48116f4ce269a8 Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Thu, 17 Mar 2016 21:08:09 +0000 Subject: [PATCH] MIPS: Fix broken malta qemu 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 Reported-by: Guenter Roeck Tested-by: Guenter Roeck Cc: Thomas Gleixner Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/12892/ Signed-off-by: Ralf Baechle --- 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 37708d9af638..27cb638f0824 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); -- 2.20.1