Re: [PATCH 09/10] KVM: x86: MMU: Move parent_pte handling from kvm_mmu_get_page() to link_shadow_page()

[Xiao Guangrong]

You can move this patch to the front of
[PATCH 08/10] KVM: x86: MMU: Use for_each_rmap_spte macro instead of pte_list_walk()

By moving kvm_mmu_mark_parents_unsync() to the behind of mmu_spte_set() (then the parent
spte is present now), you can directly clean up for_each_rmap_spte().


On 11/20/2015 04:48 PM, Takuya Yoshikawa wrote:
> Every time kvm_mmu_get_page() is called with a non-NULL parent_pte
> argument, link_shadow_page() follows that to set the parent entry so
> that the new mapping will point to the returned page table.
>
> Moving parent_pte handling there allows to clean up the code because
> parent_pte is passed to kvm_mmu_get_page() just for mark_unsync() and
> mmu_page_add_parent_pte().
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
> ---
>   arch/x86/kvm/mmu.c         | 22 ++++++++--------------
>   arch/x86/kvm/paging_tmpl.h |  6 ++----
>   2 files changed, 10 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 4e29d9a..b020323 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2107,14 +2107,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>   		if (sp->unsync_children) {
>   			kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
>   			kvm_mmu_mark_parents_unsync(sp);
> -			if (parent_pte)
> -				mark_unsync(parent_pte);
>   		} else if (sp->unsync) {
>   			kvm_mmu_mark_parents_unsync(sp);
> -			if (parent_pte)
> -				mark_unsync(parent_pte);
>   		}
> -		mmu_page_add_parent_pte(vcpu, sp, parent_pte);
>
>   		__clear_sp_write_flooding_count(sp);
>   		trace_kvm_mmu_get_page(sp, false);
> @@ -2125,8 +2120,6 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>
>   	sp = kvm_mmu_alloc_page(vcpu, direct);
>
> -	mmu_page_add_parent_pte(vcpu, sp, parent_pte);
> -
>   	sp->gfn = gfn;
>   	sp->role = role;
>   	hlist_add_head(&sp->hash_link,
> @@ -2194,7 +2187,8 @@ static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
>   	return __shadow_walk_next(iterator, *iterator->sptep);
>   }
>
> -static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp)
> +static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep,
> +			     struct kvm_mmu_page *sp)
>   {
>   	u64 spte;
>
> @@ -2205,6 +2199,11 @@ static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp)
>   	       shadow_user_mask | shadow_x_mask | shadow_accessed_mask;
>
>   	mmu_spte_set(sptep, spte);
> +
> +	if (sp->unsync_children || sp->unsync)
> +		mark_unsync(sptep);
> +
> +	mmu_page_add_parent_pte(vcpu, sp, sptep);
>   }
>
>   static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> @@ -2263,11 +2262,6 @@ static void kvm_mmu_page_unlink_children(struct kvm *kvm,
>   		mmu_page_zap_pte(kvm, sp, sp->spt + i);
>   }
>
> -static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
> -{
> -	mmu_page_remove_parent_pte(sp, parent_pte);
> -}
> -
>   static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
>   {
>   	u64 *sptep;
> @@ -2733,7 +2727,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, int write, int map_writable,
>   					      iterator.level - 1,
>   					      1, ACC_ALL, iterator.sptep);
>
> -			link_shadow_page(iterator.sptep, sp);
> +			link_shadow_page(vcpu, iterator.sptep, sp);
>   		}
>   	}
>   	return emulate;
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 11650ea..0dcf9c8 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -598,7 +598,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>   			goto out_gpte_changed;
>
>   		if (sp)
> -			link_shadow_page(it.sptep, sp);
> +			link_shadow_page(vcpu, it.sptep, sp);
>   	}
>
>   	for (;
> @@ -618,7 +618,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>
>   		sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1,
>   				      true, direct_access, it.sptep);
> -		link_shadow_page(it.sptep, sp);
> +		link_shadow_page(vcpu, it.sptep, sp);
>   	}
>
>   	clear_sp_write_flooding_count(it.sptep);
> @@ -629,8 +629,6 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>   	return emulate;
>
>   out_gpte_changed:
> -	if (sp)
> -		kvm_mmu_put_page(sp, it.sptep);
>   	kvm_release_pfn_clean(pfn);
>   	return 0;
>   }
--
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