Re: [PATCH v4 18/20] KVM: x86/mmu: Refactor drop_large_spte()

[Sean Christopherson <seanjc@google.com>]

On Fri, Apr 22, 2022, David Matlack wrote:
> drop_large_spte() drops a large SPTE if it exists and then flushes TLBs.
> Its helper function, __drop_large_spte(), does the drop without the
> flush.
> 
> In preparation for eager page splitting, which will need to sometimes
> flush when dropping large SPTEs (and sometimes not), push the flushing
> logic down into __drop_large_spte() and add a bool parameter to control
> it.
> 
> No functional change intended.
> 
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 29 +++++++++++++++--------------
>  1 file changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 479c581e8a96..a5961c17eb36 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1183,28 +1183,29 @@ static void drop_spte(struct kvm *kvm, u64 *sptep)
>  		rmap_remove(kvm, sptep);
>  }
>  
> -
> -static bool __drop_large_spte(struct kvm *kvm, u64 *sptep)
> +static void __drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush)
>  {
> -	if (is_large_pte(*sptep)) {
> -		WARN_ON(sptep_to_sp(sptep)->role.level == PG_LEVEL_4K);
> -		drop_spte(kvm, sptep);
> -		return true;
> -	}
> +	struct kvm_mmu_page *sp;
>  
> -	return false;
> -}
> +	if (!is_large_pte(*sptep))
> +		return;
>  
> -static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
> -{
> -	if (__drop_large_spte(vcpu->kvm, sptep)) {
> -		struct kvm_mmu_page *sp = sptep_to_sp(sptep);
> +	sp = sptep_to_sp(sptep);
> +	WARN_ON(sp->role.level == PG_LEVEL_4K);
>  
> -		kvm_flush_remote_tlbs_with_address(vcpu->kvm, sp->gfn,
> +	drop_spte(kvm, sptep);
> +
> +	if (flush) {

Unnecessary curly braces.

> +		kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
>  			KVM_PAGES_PER_HPAGE(sp->role.level));
>  	}
>  }
>  
> +static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
> +{
> +	return __drop_large_spte(vcpu->kvm, sptep, true);
> +}
> +
>  /*
>   * Write-protect on the specified @sptep, @pt_protect indicates whether
>   * spte write-protection is caused by protecting shadow page table.
> -- 
> 2.36.0.rc2.479.g8af0fa9b8e-goog
>