Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932200AbaFYMuj (ORCPT ); Wed, 25 Jun 2014 08:50:39 -0400 Received: from mail-vc0-f171.google.com ([209.85.220.171]:60974 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932160AbaFYMud (ORCPT ); Wed, 25 Jun 2014 08:50:33 -0400 MIME-Version: 1.0 In-Reply-To: <1403688530-23273-4-git-send-email-marc.zyngier@arm.com> References: <1403688530-23273-1-git-send-email-marc.zyngier@arm.com> <1403688530-23273-4-git-send-email-marc.zyngier@arm.com> From: Rob Herring Date: Wed, 25 Jun 2014 07:50:12 -0500 Message-ID: Subject: Re: [RFC PATCH 3/9] irqchip: GIC: Convert to EOImode == 1 To: Marc Zyngier Cc: "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Catalin Marinas , Thomas Gleixner , Will Deacon , Christoffer Dall , eric.auger@linaro.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 25, 2014 at 4:28 AM, 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. Why not fix-up the size so the feature can be enabled? Rob -- 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/