From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DCF0CCA479 for ; Mon, 18 Jul 2022 14:11:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235159AbiGROL1 (ORCPT ); Mon, 18 Jul 2022 10:11:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231625AbiGROLZ (ORCPT ); Mon, 18 Jul 2022 10:11:25 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87A1E2714C; Mon, 18 Jul 2022 07:11:24 -0700 (PDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 26IDnlU5014351; Mon, 18 Jul 2022 14:11:23 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : from : to : cc : references : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=tG4x1luIWgAiy5cC05XNkiErNbUMWb1doBHkaeJaKRY=; b=cU/tF86MyRs+/zdd7/Eg/JObLi9LLbo9OmHomgDE6zealFx8XgG2/uEHv+sclbALpK6O hZyF6Mqxle0dwee2wW1DTA7bqIHd0B9PVqPCDOdWaHKdILzlxHEugp/5N9WoAbJnsVCk U7Cj3nalAS1kW13U23KCa1OiB+/U2VU/KKxl+MXDgs/QDXY+rl9AcCTrzCDi9G5BMb3r 4il3y7orD+OkYSCQHccT4f6UEB5Q2vH2wQDpibG7J5ja1zQJo+PhN9ZuIGYefBJ51FHv Fng5O4yTgMSar183Q2pJHpG+nNcD+S9hslDXRXZRCtePDSOt8dSUVAXdhvEgbr8KV9ax jw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3hd8r5rnkw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Jul 2022 14:11:23 +0000 Received: from m0098420.ppops.net (m0098420.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 26IDoplL024256; Mon, 18 Jul 2022 14:11:23 GMT Received: from ppma03wdc.us.ibm.com (ba.79.3fa9.ip4.static.sl-reverse.com [169.63.121.186]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3hd8r5rnkm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Jul 2022 14:11:23 +0000 Received: from pps.filterd (ppma03wdc.us.ibm.com [127.0.0.1]) by ppma03wdc.us.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 26IE7DEl030656; Mon, 18 Jul 2022 14:11:22 GMT Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by ppma03wdc.us.ibm.com with ESMTP id 3hbmy8w8gh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Jul 2022 14:11:22 +0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 26IEBLGi22217074 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 18 Jul 2022 14:11:21 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C9078B2064; Mon, 18 Jul 2022 14:11:21 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 30AD1B2076; Mon, 18 Jul 2022 14:11:21 +0000 (GMT) Received: from [9.160.177.24] (unknown [9.160.177.24]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 18 Jul 2022 14:11:21 +0000 (GMT) Message-ID: <2517bed8-fc68-bcc5-b4f3-09d493c46a04@linux.ibm.com> Date: Mon, 18 Jul 2022 10:11:20 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [RFC] kvm: reverse call order of kvm_arch_destroy_vm() and kvm_destroy_devices() Content-Language: en-US From: Anthony Krowiak To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: jjherne@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, mjrosato@linux.ibm.com, pasic@linux.ibm.com, pbonzini@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, david@redhat.com References: <20220705185430.499688-1-akrowiak@linux.ibm.com> In-Reply-To: <20220705185430.499688-1-akrowiak@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 2or0GRyPebhYNPOUJqeM8h-9pDhMpYrQ X-Proofpoint-GUID: Ritu6lKGmEgCMCmYWFw2wDW5cDBoLi4D X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-18_12,2022-07-18_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 bulkscore=0 phishscore=0 impostorscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207180061 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org PING! On 7/5/22 2:54 PM, Tony Krowiak wrote: > There is a new requirement for s390 secure execution guests that the > hypervisor ensures all AP queues are reset and disassociated from the > KVM guest before the secure configuration is torn down. It is the > responsibility of the vfio_ap device driver to handle this. > > Prior to commit ("vfio: remove VFIO_GROUP_NOTIFY_SET_KVM"), > the driver reset all AP queues passed through to a KVM guest when notified > that the KVM pointer was being set to NULL. Subsequently, the AP queues > are only reset when the fd for the mediated device used to pass the queues > through to the guest is closed (the vfio_ap_mdev_close_device() callback). > This is not a problem when userspace is well-behaved and uses the > KVM_DEV_VFIO_GROUP_DEL attribute to remove the VFIO group; however, if > userspace for some reason does not close the mdev fd, a secure execution > guest will tear down its configuration before the AP queues are > reset because the teardown is done in the kvm_arch_destroy_vm function > which is invoked prior to vm_destroy_devices. > > This patch proposes a simple solution; rather than introducing a new > notifier into vfio or callback into KVM, what aoubt reversing the order > in which the kvm_arch_destroy_vm and kvm_destroy_devices are called. In > some very limited testing (i.e., the automated regression tests for > the vfio_ap device driver) this did not seem to cause any problems. > > The question remains, is there a good technical reason why the VM > is destroyed before the devices it is using? This is not intuitive, so > this is a request for comments on this proposed patch. The assumption > here is that the medev fd will get closed when the devices are destroyed. > > Signed-off-by: Tony Krowiak > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index a49df8988cd6..edaf2918be9b 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1248,8 +1248,8 @@ static void kvm_destroy_vm(struct kvm *kvm) > #else > kvm_flush_shadow_all(kvm); > #endif > - kvm_arch_destroy_vm(kvm); > kvm_destroy_devices(kvm); > + kvm_arch_destroy_vm(kvm); > for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > kvm_free_memslots(kvm, &kvm->__memslots[i][0]); > kvm_free_memslots(kvm, &kvm->__memslots[i][1]);