linux-kernel - Re: [PATCH v2 23/28] KVM: x86/mmu: Allow parallel page faults for the TDP MMU

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Date:   Wed, 3 Feb 2021 19:30:50 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ben Gardon <bgardon@...gle.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 23/28] KVM: x86/mmu: Allow parallel page faults for the
 TDP MMU

On 03/02/21 18:46, Ben Gardon wrote:
> enum kvm_mmu_lock_mode lock_mode =
> get_mmu_lock_mode_for_root(vcpu->kvm, vcpu->arch.mmu->root_hpa);
> ....
> kvm_mmu_lock_for_mode(lock_mode);
> 
> Not sure if either of those are actually clearer, but the latter
> trends in the direction the RCF took, having an enum to capture
> read/write and whether or not yo yield in a lock mode parameter.

Could be a possibility.  Also:

enum kvm_mmu_lock_mode lock_mode =
   kvm_mmu_lock_for_root(vcpu->kvm, vcpu->arch.mmu->root_hpa);

kvm_mmu_unlock(vcpu->kvm, lock_mode);

Anyway it can be done on top.

Paolo