Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932215AbaFYOq4 (ORCPT ); Wed, 25 Jun 2014 10:46:56 -0400 Received: from fw-tnat.austin.arm.com ([217.140.110.23]:18217 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756294AbaFYOqz (ORCPT ); Wed, 25 Jun 2014 10:46:55 -0400 Message-ID: <53AAE0D3.8030008@arm.com> Date: Wed, 25 Jun 2014 15:46:43 +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: Peter Maydell CC: "kvmarm@lists.cs.columbia.edu" , arm-mail-list , lkml - Kernel Mailing List , Catalin Marinas , Thomas Gleixner , Will Deacon , Christoffer Dall , Eric Auger 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=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/06/14 15:06, Peter Maydell wrote: > On 25 June 2014 10:28, Marc Zyngier wrote: >> 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. > > Does that mean you guarantee not to write to the DEACTIVATE register > if not booted in Hyp mode? I ask because QEMU's GIC emulation doesn't > emulate that register, so it would be useful to know if this patch > means newer kernels are going to fall over under TCG QEMU... So far, I only plan to support it when booted in HYP. But it may be that the split prio-drop/deactivate is also beneficial to threaded interrupts, saving the writes to the distributor to mask/unmask. That would require to be a bit more subtle in identifying a GICv2 implementation (DT binding, probably). 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/