4.17-stable review patch. If anyone has any objections, please let me know.
------------------ From: Marc Zyngier <[email protected]> [ Upstream commit 82f499c8811149069ec958b72a86643a7a289b25 ] Enabling LPIs was made a lot stricter recently, by checking that they are disabled before enabling them. By doing so, the CPU hotplug case was missed altogether, which leaves LPIs enabled on hotplug off (expecting the CPU to eventually come back), and won't write a different value anyway on hotplug on. So skip that check if that particular case is detected Fixes: 6eb486b66a30 ("irqchip/gic-v3: Ensure GICR_CTLR.EnableLPI=0 is observed before enabling") Reported-by: Sumit Garg <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Sumit Garg <[email protected]> Cc: Jason Cooper <[email protected]> Cc: Alexandre Belloni <[email protected]> Cc: Yang Yingliang <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/irqchip/irq-gic-v3-its.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -3405,6 +3405,16 @@ static int redist_disable_lpis(void) u64 timeout = USEC_PER_SEC; u64 val; + /* + * If coming via a CPU hotplug event, we don't need to disable + * LPIs before trying to re-enable them. They are already + * configured and all is well in the world. Detect this case + * by checking the allocation of the pending table for the + * current CPU. + */ + if (gic_data_rdist()->pend_page) + return 0; + if (!gic_rdists_supports_plpis()) { pr_info("CPU%d: LPIs not supported\n", smp_processor_id()); return -ENXIO;
