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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2B51C433F5 for ; Tue, 4 Sep 2018 07:44:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5787F20661 for ; Tue, 4 Sep 2018 07:44:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5787F20661 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=de.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbeIDMHw (ORCPT ); Tue, 4 Sep 2018 08:07:52 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:39316 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725990AbeIDMHw (ORCPT ); Tue, 4 Sep 2018 08:07:52 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w847eCu3159541 for ; Tue, 4 Sep 2018 03:43:57 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0b-001b2d01.pphosted.com with ESMTP id 2m9m1u4jux-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 04 Sep 2018 03:43:56 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 4 Sep 2018 08:43:51 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w847hpcI22348014 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 4 Sep 2018 07:43:51 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 361E75204E; Tue, 4 Sep 2018 10:43:44 +0100 (BST) Received: from oc7455500831.ibm.com (unknown [9.152.224.41]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 9D4D052054; Tue, 4 Sep 2018 10:43:43 +0100 (BST) Subject: Re: [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct To: Fengguang Wu , Nikita Leshenko Cc: akpm@linux-foundation.org, linux-mm@kvack.org, dongx.peng@intel.com, jingqi.liu@intel.com, eddie.dong@intel.com, dave.hansen@intel.com, ying.huang@intel.com, bgregg@netflix.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <0ef9ccdc-3eae-f0b9-5304-8552cb94d166@de.ibm.com> <20180904002818.nq2ejxlsn4o34anl@wfg-t540p.sh.intel.com> <20180904004621.aqhemgpefwtq3kif@wfg-t540p.sh.intel.com> <20180904071552.f4cmxo7hwtjw22dc@wfg-t540p.sh.intel.com> From: Christian Borntraeger Openpgp: preference=signencrypt Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180904071552.f4cmxo7hwtjw22dc@wfg-t540p.sh.intel.com> Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18090407-0020-0000-0000-000002C0D441 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18090407-0021-0000-0000-0000210DF852 Message-Id: <45efb10a-a55a-b917-589c-de55e88ec18f@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-04_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809040081 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/04/2018 09:15 AM, Fengguang Wu wrote: > On Tue, Sep 04, 2018 at 08:37:03AM +0200, Nikita Leshenko wrote: >> On 4 Sep 2018, at 2:46, Fengguang Wu wrote: >>> >>> Here it goes: >>> >>> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >>> index 99ce070e7dcb..27c5446f3deb 100644 >>> --- a/include/linux/mm_types.h >>> +++ b/include/linux/mm_types.h >>> @@ -27,6 +27,7 @@ typedef int vm_fault_t; >>> struct address_space; >>> struct mem_cgroup; >>> struct hmm; >>> +struct kvm; >>> /* >>> * Each physical page in the system has a struct page associated with >>> @@ -489,10 +490,19 @@ struct mm_struct { >>>     /* HMM needs to track a few things per mm */ >>>     struct hmm *hmm; >>> #endif >>> +#if IS_ENABLED(CONFIG_KVM) >>> +    struct kvm *kvm; >>> +#endif >>> } __randomize_layout; >>> extern struct mm_struct init_mm; >>> +#if IS_ENABLED(CONFIG_KVM) >>> +static inline struct kvm *mm_kvm(struct mm_struct *mm) { return mm->kvm; } >>> +#else >>> +static inline struct kvm *mm_kvm(struct mm_struct *mm) { return NULL; } >>> +#endif >>> + >>> static inline void mm_init_cpumask(struct mm_struct *mm) >>> { >>> #ifdef CONFIG_CPUMASK_OFFSTACK >>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >>> index 0c483720de8d..dca6156a7b35 100644 >>> --- a/virt/kvm/kvm_main.c >>> +++ b/virt/kvm/kvm_main.c >>> @@ -3892,7 +3892,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) >>>     if (type == KVM_EVENT_CREATE_VM) { >>>         add_uevent_var(env, "EVENT=create"); >>>         kvm->userspace_pid = task_pid_nr(current); >>> -        current->kvm = kvm; >>> +        current->mm->kvm = kvm; >> I think you also need to reset kvm to NULL once the VM is >> destroyed, otherwise it would point to dangling memory. > > Good point! Here is the incremental patch: > > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3894,6 +3894,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) >                kvm->userspace_pid = task_pid_nr(current); >                current->mm->kvm = kvm; >        } else if (type == KVM_EVENT_DESTROY_VM) { > +               current->mm->kvm = NULL; >                add_uevent_var(env, "EVENT=destroy"); >        } >        add_uevent_var(env, "PID=%d", kvm->userspace_pid); I think you should put both code snippets somewhere else. This has probably nothing to do with the uevent. Instead this should go into kvm_destroy_vm and kvm_create_vm. Make sure to take care of the error handling. Can you point us to the original discussion about the why and what you are trying to achieve?