linux-kernel - Re: [PATCH 08/12] KVM: X86/MMU: Remove the useless idx from struct kvm_mmu

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Date:   Tue, 19 Jul 2022 20:31:04 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>
Subject: Re: [PATCH 08/12] KVM: X86/MMU: Remove the useless idx from struct
 kvm_mmu_pages

It's arguably not useless, e.g. it's still used for a sanity check.  Not sure
how to word that though.  Maybe?

  KVM: x86/mmu: Drop no-longer-necessary mmu_page_and_offset.idx

On Sun, Jun 05, 2022, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@...group.com>
> 
> The value is only set but never really used.

Please elaborate on why it's no longer truly used.  Something like:

  Drop mmu_page_and_offset.idx, it's no longer strictly necessary now that
  KVM doesn't recurse up the walk to clear unsync information in parents.
  The field is still used for a sanity check, but that sanity check will
  soon be made obsolete by further simplifying the gathering of unsync
  shadow pages