linux-kernel - Re: [PATCH RESEND v2 03/17] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP

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Message-ID: <20200108191512.GF7096@xz-x1>
Date:   Wed, 8 Jan 2020 14:15:12 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Christophe de Dinechin <dinechin@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH RESEND v2 03/17] KVM: X86: Don't track dirty for
 KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR]

On Wed, Jan 08, 2020 at 06:46:30PM +0100, Paolo Bonzini wrote:
> On 23/12/19 21:10, Peter Xu wrote:
> >> Yes, kvm->slots_lock is taken by x86_set_memory_region.  We need to move
> >> that to the callers, of which several are already taking the lock (all
> >> except vmx_set_tss_addr and kvm_arch_destroy_vm).
> > OK, will do.  I'll directly replace the x86_set_memory_region() calls
> > in kvm_arch_destroy_vm() to be __x86_set_memory_region() since IIUC
> > the slots_lock is helpless when destroying the vm... then drop the
> > x86_set_memory_region() helper in the next version.  Thanks,
> 
> Be careful because it may cause issues with lockdep.  Better just take
> the lock.

But you seemed to have fixed that already? :)

3898da947bba ("KVM: avoid using rcu_dereference_protected", 2017-08-02)

And this path is after kvm_destroy_vm() so kvm->users_count should be 0.
Or I feel like we need to have more places to take the lock..

-- 
Peter Xu