linux-kernel - Re: [KVM] d3750a0923: WARNING:possible_circular_locking_dependency

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Date:   Mon, 6 Dec 2021 07:55:18 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     kernel test robot <oliver.sang@...el.com>,
        David Matlack <dmatlack@...gle.com>
Cc:     0day robot <lkp@...el.com>, LKML <linux-kernel@...r.kernel.org>,
        lkp@...ts.01.org, kvm@...r.kernel.org,
        Ben Gardon <bgardon@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Janis Schoetterl-Glausch <scgl@...ux.vnet.ibm.com>,
        Junaid Shahid <junaids@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Harish Barathvajasankar <hbarath@...gle.com>,
        Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>
Subject: Re: [KVM] d3750a0923:
 WARNING:possible_circular_locking_dependency_detected

On 12/5/21 14:30, kernel test robot wrote:
>
> Chain exists of:
>   fs_reclaim --> mmu_notifier_invalidate_range_start --> &(kvm)->mmu_lock
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&(kvm)->mmu_lock);
>                                lock(mmu_notifier_invalidate_range_start);
>                                lock(&(kvm)->mmu_lock);
>   lock(fs_reclaim);
>

David, this is yours; basically, kvm_mmu_topup_memory_cache must be 
called outside the mmu_lock.

Paolo