KVM: MMU: Replace walk_shadow() by for_each_shadow_entry() in fetch()

Effectively reverting to the pre walk_shadow() version -- but now
with the reusable for_each().
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/paging_tmpl.h

@@ -283,35 +283,41 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
 /*
  * Fetch a shadow pte for a specific level in the paging hierarchy.
  */
-static int FNAME(shadow_walk_entry)(struct kvm_shadow_walk *_sw,
-				    struct kvm_vcpu *vcpu, u64 addr,
-				    u64 *sptep, int level)
+static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
+			 struct guest_walker *gw,
+			 int user_fault, int write_fault, int largepage,
+			 int *ptwrite, pfn_t pfn)
 {
-	struct shadow_walker *sw =
-		container_of(_sw, struct shadow_walker, walker);
-	struct guest_walker *gw = sw->guest_walker;
 	unsigned access = gw->pt_access;
 	struct kvm_mmu_page *shadow_page;
-	u64 spte;
+	u64 spte, *sptep;
 	int metaphysical;
 	gfn_t table_gfn;
 	int r;
+	int level;
 	pt_element_t curr_pte;
+	struct kvm_shadow_walk_iterator iterator;
 
+	if (!is_present_pte(gw->ptes[gw->level - 1]))
+		return NULL;
+
+	for_each_shadow_entry(vcpu, addr, iterator) {
+		level = iterator.level;
+		sptep = iterator.sptep;
 		if (level == PT_PAGE_TABLE_LEVEL
-	    || (sw->largepage && level == PT_DIRECTORY_LEVEL)) {
-		mmu_set_spte(vcpu, sptep, access, gw->pte_access & access,
-			     sw->user_fault, sw->write_fault,
+		    || (largepage && level == PT_DIRECTORY_LEVEL)) {
+			mmu_set_spte(vcpu, sptep, access,
+				     gw->pte_access & access,
+				     user_fault, write_fault,
 				     gw->ptes[gw->level-1] & PT_DIRTY_MASK,
-			     sw->ptwrite, sw->largepage,
+				     ptwrite, largepage,
 				     gw->ptes[gw->level-1] & PT_GLOBAL_MASK,
-			     gw->gfn, sw->pfn, false);
-		sw->sptep = sptep;
-		return 1;
+				     gw->gfn, pfn, false);
+			break;
 		}
 
 		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
-		return 0;
+			continue;
 
 		if (is_large_pte(*sptep)) {
 			set_shadow_pte(sptep, shadow_trap_nonpresent_pte);
@@ -319,7 +325,8 @@ static int FNAME(shadow_walk_entry)(struct kvm_shadow_walk *_sw,
 			rmap_remove(vcpu->kvm, sptep);
 		}
 
-	if (level == PT_DIRECTORY_LEVEL && gw->level == PT_DIRECTORY_LEVEL) {
+		if (level == PT_DIRECTORY_LEVEL
+		    && gw->level == PT_DIRECTORY_LEVEL) {
 			metaphysical = 1;
 			if (!is_dirty_pte(gw->ptes[level - 1]))
 				access &= ~ACC_WRITE_MASK;
@@ -328,46 +335,27 @@ static int FNAME(shadow_walk_entry)(struct kvm_shadow_walk *_sw,
 			metaphysical = 0;
 			table_gfn = gw->table_gfn[level - 2];
 		}
-	shadow_page = kvm_mmu_get_page(vcpu, table_gfn, (gva_t)addr, level-1,
+		shadow_page = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
 					       metaphysical, access, sptep);
 		if (!metaphysical) {
-		r = kvm_read_guest_atomic(vcpu->kvm, gw->pte_gpa[level - 2],
+			r = kvm_read_guest_atomic(vcpu->kvm,
+						  gw->pte_gpa[level - 2],
 						  &curr_pte, sizeof(curr_pte));
 			if (r || curr_pte != gw->ptes[level - 2]) {
 				kvm_mmu_put_page(shadow_page, sptep);
-			kvm_release_pfn_clean(sw->pfn);
-			sw->sptep = NULL;
-			return 1;
+				kvm_release_pfn_clean(pfn);
+				sptep = NULL;
+				break;
 			}
 		}
 
-	spte = __pa(shadow_page->spt) | PT_PRESENT_MASK | PT_ACCESSED_MASK
+		spte = __pa(shadow_page->spt)
+			| PT_PRESENT_MASK | PT_ACCESSED_MASK
 			| PT_WRITABLE_MASK | PT_USER_MASK;
 		*sptep = spte;
-	return 0;
-}
-
-static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
-			 struct guest_walker *guest_walker,
-			 int user_fault, int write_fault, int largepage,
-			 int *ptwrite, pfn_t pfn)
-{
-	struct shadow_walker walker = {
-		.walker = { .entry = FNAME(shadow_walk_entry), },
-		.guest_walker = guest_walker,
-		.user_fault = user_fault,
-		.write_fault = write_fault,
-		.largepage = largepage,
-		.ptwrite = ptwrite,
-		.pfn = pfn,
-	};
-
-	if (!is_present_pte(guest_walker->ptes[guest_walker->level - 1]))
-		return NULL;
-
-	walk_shadow(&walker.walker, vcpu, addr);
+	}
 
-	return walker.sptep;
+	return sptep;
 }
 
 /*