linux-kernel - Re: [Patch v2 3/5] KVM: x86/mmu: Optimize SPTE change for aging gfn range

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Message-ID: <CANgfPd8NF88V+ddqeCBsz=NRgm-YV7nH1DwDhRsHpA_AnFBB7g@mail.gmail.com>
Date:   Mon, 6 Feb 2023 14:17:06 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, dmatlack@...gle.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v2 3/5] KVM: x86/mmu: Optimize SPTE change for aging gfn range

On Fri, Feb 3, 2023 at 11:28 AM Vipin Sharma <vipinsh@...gle.com> wrote:
>
> No need to check all of the conditions in __handle_changed_spte(). Aging
> a gfn range implies resetting access bit or marking spte for access
> tracking.
>
> Use atomic operation to only reset those bits. This avoids checking many
> conditions in __handle_changed_spte() API. Also, clean up code by
> removing dead code and API parameters.
>
> Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 68 ++++++++++++++------------------------
>  1 file changed, 25 insertions(+), 43 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 83f15052aa6c..18630a06fa1f 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -697,7 +697,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>
>
>  /*
> - * __tdp_mmu_set_spte - Set a TDP MMU SPTE and handle the associated bookkeeping
> + * _tdp_mmu_set_spte - Set a TDP MMU SPTE and handle the associated bookkeeping

Nit: Not sure how we got to the point of having a single and double
underscore of the function, but what do you think about just calling
this one tdp_mmu_set_spte and the other tdp_mmu_iter_set_spte?