linux-kernel - Re: [PATCH v2 1/4] KVM: x86/mmu: Add optimized helper to retrieve an SPTE's index

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Message-ID: <YrZLriNw1CElOKbz@google.com>
Date:   Fri, 24 Jun 2022 23:41:34 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] KVM: x86/mmu: Add optimized helper to retrieve an
 SPTE's index

On Fri, Jun 24, 2022 at 09:30:36PM +0000, Sean Christopherson wrote:
> Add spte_index() to dedup all the code that calculates a SPTE's index
> into its parent's page table and/or spt array.  Opportunistically tweak
> the calculation to avoid pointer arithmetic, which is subtle (subtract in
> 8-byte chunks) and less performant (requires the compiler to generate the
> subtraction).
> 
> Suggested-by: David Matlack <dmatlack@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Thanks for the cleanup. I did a git-grep to look for any other users to
convert to spte_index() and didn't find any.

Reviewed-by: David Matlack <dmatlack@...gle.com>