Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757898AbaGAIZA (ORCPT ); Tue, 1 Jul 2014 04:25:00 -0400 Received: from fw-tnat.austin.arm.com ([217.140.110.23]:56653 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757876AbaGAIYz (ORCPT ); Tue, 1 Jul 2014 04:24:55 -0400 Message-ID: <53B27049.10302@arm.com> Date: Tue, 01 Jul 2014 09:24:41 +0100 From: Marc Zyngier User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130330 Thunderbird/17.0.5 MIME-Version: 1.0 To: Stefano Stabellini CC: Anup Patel , "kvmarm@lists.cs.columbia.edu" , linux-arm-kernel , "linux-kernel@vger.kernel.org List" , Catalin Marinas , Thomas Gleixner , Will Deacon , Christoffer Dall , Eric Auger , Ian Campbell Subject: Re: [RFC PATCH 3/9] irqchip: GIC: Convert to EOImode == 1 References: <1403688530-23273-1-git-send-email-marc.zyngier@arm.com> <1403688530-23273-4-git-send-email-marc.zyngier@arm.com> In-Reply-To: X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Stefano, On 30/06/14 20:09, Stefano Stabellini wrote: > On Wed, 25 Jun 2014, Anup Patel wrote: >> Hi Marc, >> >> On Wed, Jun 25, 2014 at 2:58 PM, Marc Zyngier wrote: >>> So far, GICv2 has been used in with EOImode == 0. The effect of this >>> mode is to perform the priority drop and the deactivation of the >>> interrupt at the same time. >>> >>> While this works perfectly for Linux (we only have a single priority), >>> it causes issues when an interrupt is forwarded to a guest, and when >>> we want the guest to perform the EOI itself. >>> >>> For this case, the GIC architecture provides EOImode == 1, where: >>> - A write to the EOI register drops the priority of the interrupt and leaves >>> it active. Other interrupts at the same priority level can now be taken, >>> but the active interrupt cannot be taken again >>> - A write to the DIR marks the interrupt as inactive, meaning it can >>> now be taken again. >>> >>> We only enable this feature when booted in HYP mode. Also, as most device >>> trees are broken (they report the CPU interface size to be 4kB, while >>> the GICv2 CPU interface size is 8kB), output a warning if we're booted >>> in HYP mode, and disable the feature. >>> >>> Signed-off-by: Marc Zyngier >>> --- >>> drivers/irqchip/irq-gic.c | 61 +++++++++++++++++++++++++++++++++++++---- >>> include/linux/irqchip/arm-gic.h | 4 +++ >>> 2 files changed, 59 insertions(+), 6 deletions(-) >>> >>> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c >>> index 508b815..9295bf2 100644 >>> --- a/drivers/irqchip/irq-gic.c >>> +++ b/drivers/irqchip/irq-gic.c >>> @@ -45,6 +45,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include "irq-gic-common.h" >>> #include "irqchip.h" >>> @@ -94,6 +95,10 @@ struct irq_chip gic_arch_extn = { >>> .irq_set_wake = NULL, >>> }; >>> >>> +static struct irq_chip *gic_chip; >>> + >>> +static bool supports_deactivate = false; >>> + >>> #ifndef MAX_GIC_NR >>> #define MAX_GIC_NR 1 >>> #endif >>> @@ -185,6 +190,12 @@ static void gic_eoi_irq(struct irq_data *d) >>> writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI); >>> } >>> >>> +static void gic_eoi_dir_irq(struct irq_data *d) >>> +{ >>> + gic_eoi_irq(d); >>> + writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_DEACTIVATE); >>> +} > > Would it be better if you moved the gic_eoi_irq call earlier? Maybe > somewhere in gic_handle_irq? I'm not sure I see what we'd gain by doing so. Can you elaborate? Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/