From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f197.google.com (mail-pl1-f197.google.com [209.85.214.197]) by kanga.kvack.org (Postfix) with ESMTP id B4CE26B6C42 for ; Tue, 4 Sep 2018 03:16:00 -0400 (EDT) Received: by mail-pl1-f197.google.com with SMTP id 33-v6so1464664plf.19 for ; Tue, 04 Sep 2018 00:16:00 -0700 (PDT) Received: from mga06.intel.com (mga06.intel.com. [134.134.136.31]) by mx.google.com with ESMTPS id y22-v6si20369023pgj.436.2018.09.04.00.15.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Sep 2018 00:15:59 -0700 (PDT) Date: Tue, 4 Sep 2018 15:15:52 +0800 From: Fengguang Wu Subject: Re: [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct Message-ID: <20180904071552.f4cmxo7hwtjw22dc@wfg-t540p.sh.intel.com> References: <0ef9ccdc-3eae-f0b9-5304-8552cb94d166@de.ibm.com> <20180904002818.nq2ejxlsn4o34anl@wfg-t540p.sh.intel.com> <20180904004621.aqhemgpefwtq3kif@wfg-t540p.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Nikita Leshenko Cc: Christian Borntraeger , 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 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); Thanks, Fengguang