Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751499AbdINRGJ (ORCPT ); Thu, 14 Sep 2017 13:06:09 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38542 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751316AbdINRGI (ORCPT ); Thu, 14 Sep 2017 13:06:08 -0400 From: Marc Zyngier To: Eric Auger Cc: , , , , , , , Subject: Re: [RFC] KVM: arm/arm64: Introduce KVM_DEV_ARM_ITS_CTRL_RESET In-Reply-To: <1505379448-19583-1-git-send-email-eric.auger@redhat.com> (Eric Auger's message of "Thu, 14 Sep 2017 10:57:28 +0200") Organization: ARM Ltd References: <1505379448-19583-1-git-send-email-eric.auger@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) Date: Thu, 14 Sep 2017 18:06:06 +0100 Message-ID: <864ls5rz0h.fsf@arm.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1389 Lines: 35 On Thu, Sep 14 2017 at 10:57:28 am BST, Eric Auger wrote: > At the moment, the in-kernel emulated ITS is not properly reset. > On guest restart/reset some registers keep their old values and > internal structures like device, ITE, collection lists are not emptied. > > This may lead to various bugs. Among them, we can have incorrect state > backup or failure when saving the ITS state at early guest boot stage. > > This patch introduces a new attribute, KVM_DEV_ARM_ITS_CTRL_RESET in > the KVM_DEV_ARM_VGIC_GRP_CTRL group. > > Upon this action, we can invalidate the various memory structures > pointed by GITS_BASERn and GITS_CBASER, free the ITS internal caches > and reset the relevant registers. > > Signed-off-by: Eric Auger > > --- > > An alternative would consist in having the userspace writing > individual registers with default values: GITS_BASERn, GITS_CBASER > and GITS_CTLR. On kernel side we would reset related lists when > detecting the valid bit is set to false. I'm not sure this is necessarily a "either/or" situation. It looks to me that we're not completely doing the right thing when writing to the GITS_BASER registers, and that writing a new value (with the valid bit set or not) should have an action of some sort on the fate of the existing mappings. Thoughts? M. -- Jazz is not dead. It just smells funny.