Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754666AbdLTJe5 (ORCPT ); Wed, 20 Dec 2017 04:34:57 -0500 Received: from mail-lf0-f65.google.com ([209.85.215.65]:37744 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754235AbdLTJey (ORCPT ); Wed, 20 Dec 2017 04:34:54 -0500 X-Google-Smtp-Source: ACJfBotFFQwMA2sc22Rpim8IaKtA1ZQDRnZlV2oTi3oLxCZYQiWePb9FWHVX8TzGqKQsxDDvYIARE/3fXIVmtnkfo+4= MIME-Version: 1.0 In-Reply-To: References: <20171220091544.4467-1-ganapatrao.kulkarni@cavium.com> From: Ganapatrao Kulkarni Date: Wed, 20 Dec 2017 15:04:52 +0530 Message-ID: Subject: Re: [PATCH] irqchip/gic-v3-its: Flush GICR caching for a cross node collection move of an irq To: Marc Zyngier Cc: Ganapatrao Kulkarni , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner , jason@lakedaemon.net, catalin.marinas@arm.com, Will Deacon , jnair@caviumnetworks.com, Robert Richter , Jan.Glauber@cavium.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2433 Lines: 58 Hi Marc, On Wed, Dec 20, 2017 at 2:56 PM, Marc Zyngier wrote: > On 20/12/17 09:15, Ganapatrao Kulkarni wrote: >> When an interrupt is moved, it is possible that an implementation that >> supports caching might still have cached data for a previous >> (no longer valid) mapping of the interrupt. In particular, in a distributed >> GIC implementation like multi-socket SoC platfroms. Hence it is necessary >> to flush cached entries after cross node collection migration. >> >> Signed-off-by: Ganapatrao Kulkarni >> --- >> drivers/irqchip/irq-gic-v3-its.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c >> index 4039e64..ea849a1 100644 >> --- a/drivers/irqchip/irq-gic-v3-its.c >> +++ b/drivers/irqchip/irq-gic-v3-its.c >> @@ -1119,6 +1119,12 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, >> if (cpu != its_dev->event_map.col_map[id]) { >> target_col = &its_dev->its->collections[cpu]; >> its_send_movi(its_dev, target_col, id); >> + /* Issue INV for cross node collection move on >> + * multi socket systems. >> + */ >> + if (cpu_to_node(cpu) != >> + cpu_to_node(its_dev->event_map.col_map[id])) >> + its_send_inv(its_dev, id); >> its_dev->event_map.col_map[id] = cpu; >> irq_data_update_effective_affinity(d, cpumask_of(cpu)); >> } >> > > The MOVI command doesn't have any such requirement (it only mandates > synchronization), and doesn't say anything about distributed vs monolithic. GIC-v3 spec do mention to issue ITS INV command or a write to GICR_INVLPIR. pasting below snippet of MOVI command description. "When an interrupt is moved to a collection, it is possible that an implementation that supports speculative caching might still have cached data for a previous (no longer valid) mapping of the interrupt. Hence, implementations must take care to invalidate any data associated with an interrupt when it is moved. In particular, in a distributed implementation, the ITS must write to the appropriate GICR_* register to perform the invalidation in the redistributor." > > What am I missing? > > M. > -- > Jazz is not dead. It just smells funny... thanks Ganapat