Re: [PATCH v2 2/4] KVM: MMU: Move accessed/dirty bit checks from rmap_remove() to drop_spte()

[Lai Jiangshan <laijs@cn.fujitsu.com>]

Avi Kivity wrote:
> Since we need to make the check atomic, move it to the place that will
> set the new spte.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/mmu.c |   17 +++++++++--------
>  1 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 16cedc9..b5a2d3d 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -620,19 +620,11 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
>  	struct kvm_rmap_desc *desc;
>  	struct kvm_rmap_desc *prev_desc;
>  	struct kvm_mmu_page *sp;
> -	pfn_t pfn;
>  	gfn_t gfn;
>  	unsigned long *rmapp;
>  	int i;
>  
> -	if (!is_rmap_spte(*spte))
> -		return;
>  	sp = page_header(__pa(spte));
> -	pfn = spte_to_pfn(*spte);
> -	if (*spte & shadow_accessed_mask)
> -		kvm_set_pfn_accessed(pfn);
> -	if (is_writable_pte(*spte))
> -		kvm_set_pfn_dirty(pfn);
>  	gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
>  	rmapp = gfn_to_rmap(kvm, gfn, sp->role.level);
>  	if (!*rmapp) {
> @@ -668,6 +660,15 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
>  
>  static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)
>  {
> +	pfn_t pfn;
> +
> +	if (!is_rmap_spte(*sptep))
> +		return;

Missing __set_spte(sptep, new_spte); ?

> +	pfn = spte_to_pfn(*sptep);
> +	if (*sptep & shadow_accessed_mask)
> +		kvm_set_pfn_accessed(pfn);
> +	if (is_writable_pte(*sptep))
> +		kvm_set_pfn_dirty(pfn);
>  	rmap_remove(kvm, sptep);
>  	__set_spte(sptep, new_spte);
>  }