From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 25A7B6B6C5E for ; Tue, 4 Sep 2018 03:43:59 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id x145-v6so3246276oia.10 for ; Tue, 04 Sep 2018 00:43:59 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id r185-v6si13638519oif.34.2018.09.04.00.43.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Sep 2018 00:43:58 -0700 (PDT) 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 w847eCIx159533 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 2m9m1u4jv2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 04 Sep 2018 03:43:57 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 4 Sep 2018 08:43:55 +0100 Subject: Re: [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct 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 Date: Tue, 4 Sep 2018 09:43:50 +0200 MIME-Version: 1.0 In-Reply-To: <20180904071552.f4cmxo7hwtjw22dc@wfg-t540p.sh.intel.com> Content-Language: en-US Message-Id: <45efb10a-a55a-b917-589c-de55e88ec18f@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: 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 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 { >>> A A A A /* HMM needs to track a few things per mm */ >>> A A A A struct hmm *hmm; >>> #endif >>> +#if IS_ENABLED(CONFIG_KVM) >>> +A A A 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) >>> A A A A if (type == KVM_EVENT_CREATE_VM) { >>> A A A A A A A add_uevent_var(env, "EVENT=create"); >>> A A A A A A A kvm->userspace_pid = task_pid_nr(current); >>> -A A A A A A A current->kvm = kvm; >>> +A A A A A A A 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) > A A A A A A A A A A A A A A kvm->userspace_pid = task_pid_nr(current); > A A A A A A A A A A A A A A current->mm->kvm = kvm; > A A A A A A } else if (type == KVM_EVENT_DESTROY_VM) { > +A A A A A A A A A A A A A A current->mm->kvm = NULL; > A A A A A A A A A A A A A A add_uevent_var(env, "EVENT=destroy"); > A A A A A A } > A A A A A A 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?