From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [RFC] KVM: arm/arm64: Introduce KVM_DEV_ARM_ITS_CTRL_RESET Date: Thu, 14 Sep 2017 18:06:06 +0100 Message-ID: <864ls5rz0h.fsf@arm.com> References: <1505379448-19583-1-git-send-email-eric.auger@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , , , , , , To: Eric Auger Return-path: 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") Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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.