linux-kernel - Re: [PATCH v2 24/28] KVM: x86/mmu: Allow zap gfn range to operate under the mmu read lock

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Message-ID: <CANgfPd9OTKUJfnuRtMguC7kBf1GZz5Ba0yT1ssX29YQ2Zm54aA@mail.gmail.com>
Date:   Wed, 3 Feb 2021 10:31:06 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>
Subject: Re: [PATCH v2 24/28] KVM: x86/mmu: Allow zap gfn range to operate
 under the mmu read lock

On Wed, Feb 3, 2021 at 3:26 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 02/02/21 19:57, Ben Gardon wrote:
> > +#ifdef CONFIG_LOCKDEP
> > +     if (shared)
> > +             lockdep_assert_held_read(&kvm->mmu_lock);
> > +     else
> > +             lockdep_assert_held_write(&kvm->mmu_lock);
> > +#endif /* CONFIG_LOCKDEP */
>
> Also, there's no need for the #ifdef here.

I agree, I must have misinterpreted some feedback on a previous commit
and gone overboard with it.


> Do we want a helper
> kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm, bool shared)?

There are only two places that try to assert both ways as far as I can
see on a cursory check, but it couldn't hurt.

>
> Paolo
>