From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH v6 8/9] KVM: arm/arm64: Document KVM_DEV_ARM_ITS_CTRL_RESET Date: Mon, 30 Oct 2017 03:21:53 +0000 Message-ID: <8660ax7226.fsf@arm.com> References: <1509031391-4407-1-git-send-email-eric.auger@redhat.com> <1509031391-4407-9-git-send-email-eric.auger@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, cdall@linaro.org, andre.przywara@arm.com, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, wu.wubin@huawei.com, eric.auger.pro@gmail.com To: Eric Auger Return-path: In-Reply-To: <1509031391-4407-9-git-send-email-eric.auger@redhat.com> (Eric Auger's message of "Thu, 26 Oct 2017 17:23:10 +0200") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Thu, Oct 26 2017 at 6:23:10 pm 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, and collection lists are not > freed. > > 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 documents a new attribute, KVM_DEV_ARM_ITS_CTRL_RESET in > the KVM_DEV_ARM_VGIC_GRP_CTRL group. > > Upon this action, we can reset registers and especially those > pointing to tables previously allocated by the guest and free > the internal data structures storing the list of devices, collections > and lpis. > > The usual approach for device reset of having userspace write > the reset values of the registers to the kernel via the register > read/write APIs doesn't work for the ITS because it has some > internal state (caches) which is not exposed as registers, > and there is no register interface for "drop cached data without > writing it back to RAM". So we need a KVM API which mimics the > hardware's reset line, to provide the equivalent behaviour to > a "pull the power cord out of the back of the machine" reset. > > Signed-off-by: Eric Auger > Reported-by: wanghaibin Reviewed-by: Marc Zyngier M. -- Jazz is not dead. It just smells funny.