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

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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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