From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:3024 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725874AbgLMXOA (ORCPT ); Sun, 13 Dec 2020 18:14:00 -0500 Date: Mon, 14 Dec 2020 00:13:10 +0100 From: Halil Pasic Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated Message-ID: <20201214001310.2cb6f1ff.pasic@linux.ibm.com> In-Reply-To: References: <20201202234101.32169-1-akrowiak@linux.ibm.com> <20201208014018.3f89527f.pasic@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit List-ID: To: Tony Krowiak Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, alex.williamson@redhat.com, kwankhede@nvidia.com, david@redhat.com On Fri, 11 Dec 2020 16:08:53 -0500 Tony Krowiak wrote: > >>> +static void vfio_ap_mdev_put_kvm(struct ap_matrix_mdev *matrix_mdev) > >>> +{ > >>> + if (matrix_mdev->kvm) { > >>> + kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > >>> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; > >>> + vfio_ap_mdev_reset_queues(matrix_mdev->mdev); > >> This reset probably does not belong here since there is no > >> reason to reset the queues in the group notifier (see below). > > What about kvm_s390_gisc_unregister()? That needs a valid kvm > > pointer, or? Or is it OK to not pair a kvm_s390_gisc_register() > > with an kvm_s390_gisc_unregister()? > > I probably should have been more specific about what I meant. > I was thinking that the reset should not be dependent upon > whether there is a KVM pointer or not since this function is > also called from the release callback. On the other hand, > the vfio_ap_mdev_reset_queues function calls the > vfio_ap_irq_disable (AQIC) function after each queue is reset. > The vfio_ap_irq_disable function also cleans up the AQIC > resources which requires that the KVM point is valid, so if > the vfio_ap_reset_queues function is not called with a > valid KVM pointer, that could result in an exception. > > The thing is, it is unnecessary to disable interrupts after > resetting a queue because the reset disables interrupts, > so I think I should include a patch for this fix that does the > following: > > 1. Removes the disabling of interrupts subsequent to resetting >     a queue. > 2. Includes the cleanup of AQIC resources when a queue is >     reset if a KVM pointer is present. Sounds like a plan. I see, in your v2 vfio_ap_mdev_unset_kvm() does call vfio_ap_mdev_reset_queues() even when called from the group notifier. I also like that the cleanup of AQIC resources is a part of queue_reset. In fact I asked a while ago (Message-ID: <20201027074846.30ee0ddc.pasic@linux.ibm.com> in October) to make vfio_ap_mdev_reset_queue() call vfio_ap_free_aqic_resources(q). Regards, Halil