Re: [PATCH v3 12/28] KVM: x86/mmu: Refactor low-level TDP MMU set SPTE helper to take raw vals

[Mingwei Zhang <mizhang@google.com>]

On Sat, Feb 26, 2022, Sean Christopherson wrote:
> Refactor __tdp_mmu_set_spte() to work with raw values instead of a
> tdp_iter objects so that a future patch can modify SPTEs without doing a
> walk, and without having to synthesize a tdp_iter.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Reviewed-by: Ben Gardon <bgardon@google.com>

Reviewed-by: Mingwei Zhang <mizhang@google.com>

> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 51 +++++++++++++++++++++++---------------
>  1 file changed, 31 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 1dcdf1a4fcc1..9e8ba6f12ebf 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -617,9 +617,13 @@ 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
> - * @kvm: kvm instance
> - * @iter: a tdp_iter instance currently on the SPTE that should be set
> - * @new_spte: The value the SPTE should be set to
> + * @kvm:	      KVM instance
> + * @as_id:	      Address space ID, i.e. regular vs. SMM
> + * @sptep:	      Pointer to the SPTE
> + * @old_spte:	      The current value of the SPTE
> + * @new_spte:	      The new value that will be set for the SPTE
> + * @gfn:	      The base GFN that was (or will be) mapped by the SPTE
> + * @level:	      The level _containing_ the SPTE (its parent PT's level)
>   * @record_acc_track: Notify the MM subsystem of changes to the accessed state
>   *		      of the page. Should be set unless handling an MMU
>   *		      notifier for access tracking. Leaving record_acc_track
> @@ -631,12 +635,10 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>   *		      Leaving record_dirty_log unset in that case prevents page
>   *		      writes from being double counted.
>   */
> -static inline void __tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
> -				      u64 new_spte, bool record_acc_track,
> -				      bool record_dirty_log)
> +static void __tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
> +			       u64 old_spte, u64 new_spte, gfn_t gfn, int level,
> +			       bool record_acc_track, bool record_dirty_log)
>  {
> -	WARN_ON_ONCE(iter->yielded);
> -
>  	lockdep_assert_held_write(&kvm->mmu_lock);
>  
>  	/*
> @@ -646,39 +648,48 @@ static inline void __tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
>  	 * should be used. If operating under the MMU lock in write mode, the
>  	 * use of the removed SPTE should not be necessary.
>  	 */
> -	WARN_ON(is_removed_spte(iter->old_spte) || is_removed_spte(new_spte));
> +	WARN_ON(is_removed_spte(old_spte) || is_removed_spte(new_spte));
>  
> -	kvm_tdp_mmu_write_spte(iter->sptep, new_spte);
> +	kvm_tdp_mmu_write_spte(sptep, new_spte);
> +
> +	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false);
>  
> -	__handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
> -			      new_spte, iter->level, false);
>  	if (record_acc_track)
> -		handle_changed_spte_acc_track(iter->old_spte, new_spte,
> -					      iter->level);
> +		handle_changed_spte_acc_track(old_spte, new_spte, level);
>  	if (record_dirty_log)
> -		handle_changed_spte_dirty_log(kvm, iter->as_id, iter->gfn,
> -					      iter->old_spte, new_spte,
> -					      iter->level);
> +		handle_changed_spte_dirty_log(kvm, as_id, gfn, old_spte,
> +					      new_spte, level);
> +}
> +
> +static inline void _tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
> +				     u64 new_spte, bool record_acc_track,
> +				     bool record_dirty_log)
> +{
> +	WARN_ON_ONCE(iter->yielded);
> +
> +	__tdp_mmu_set_spte(kvm, iter->as_id, iter->sptep, iter->old_spte,
> +			   new_spte, iter->gfn, iter->level,
> +			   record_acc_track, record_dirty_log);
>  }
>  
>  static inline void tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter,
>  				    u64 new_spte)
>  {
> -	__tdp_mmu_set_spte(kvm, iter, new_spte, true, true);
> +	_tdp_mmu_set_spte(kvm, iter, new_spte, true, true);
>  }
>  
>  static inline void tdp_mmu_set_spte_no_acc_track(struct kvm *kvm,
>  						 struct tdp_iter *iter,
>  						 u64 new_spte)
>  {
> -	__tdp_mmu_set_spte(kvm, iter, new_spte, false, true);
> +	_tdp_mmu_set_spte(kvm, iter, new_spte, false, true);
>  }
>  
>  static inline void tdp_mmu_set_spte_no_dirty_log(struct kvm *kvm,
>  						 struct tdp_iter *iter,
>  						 u64 new_spte)
>  {
> -	__tdp_mmu_set_spte(kvm, iter, new_spte, true, false);
> +	_tdp_mmu_set_spte(kvm, iter, new_spte, true, false);
>  }
>  
>  #define tdp_root_for_each_pte(_iter, _root, _start, _end) \
> -- 
> 2.35.1.574.g5d30c73bfb-goog
>