linux-kernel - Re: [PATCH 24/24] kvm: x86/mmu: Allow parallel page faults for the TDP MMU

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Message-ID: <8079ca49-d9fe-94ae-9e6c-ebe6e8e1035d@redhat.com>
Date:   Tue, 26 Jan 2021 14:37:39 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     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 24/24] kvm: x86/mmu: Allow parallel page faults for the
 TDP MMU

On 12/01/21 19:10, Ben Gardon wrote:
> +	if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
> +		kvm_mmu_lock_shared(vcpu->kvm);
> +	else
> +		kvm_mmu_lock(vcpu->kvm);

Perhaps the better API would be kvm_mmu_lock/unlock_root; not exposing 
kvm_mmu_lock/unlock_shared and kvm_mmu_lock/unlock_exclusive at all, 
just like you use rwlock_needbreak directly in kvm_mmu_lock_needbreak.

Paolo