KVM: MMU: Add for_each_shadow_entry(), a simpler alternative to walk_shadow()

Using a for_each loop style removes the need to write callback and nasty
casts.

Implement the walk_shadow() using the for_each_shadow_entry().

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 49 insertions, 20 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5f03ec324e35..c669f2af1d12 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -150,6 +150,20 @@ struct kvm_shadow_walk {
                      u64 addr, u64 *spte, int level);
 };
 
+struct kvm_shadow_walk_iterator {
+        u64 addr;
+        hpa_t shadow_addr;
+        int level;
+        u64 *sptep;
+        unsigned index;
+};
+
+#define for_each_shadow_entry(_vcpu, _addr, _walker)    \
+        for (shadow_walk_init(&(_walker), _vcpu, _addr);        \
+             shadow_walk_okay(&(_walker));                      \
+             shadow_walk_next(&(_walker)))
+
+
 struct kvm_unsync_walk {
         int (*entry) (struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk);
 };
@@ -1254,33 +1268,48 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
         return sp;
 }
 
+static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator,
+                             struct kvm_vcpu *vcpu, u64 addr)
+{
+        iterator->addr = addr;
+        iterator->shadow_addr = vcpu->arch.mmu.root_hpa;
+        iterator->level = vcpu->arch.mmu.shadow_root_level;
+        if (iterator->level == PT32E_ROOT_LEVEL) {
+                iterator->shadow_addr
+                        = vcpu->arch.mmu.pae_root[(addr >> 30) & 3];
+                iterator->shadow_addr &= PT64_BASE_ADDR_MASK;
+                --iterator->level;
+                if (!iterator->shadow_addr)
+                        iterator->level = 0;
+        }
+}
+
+static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
+{
+        if (iterator->level < PT_PAGE_TABLE_LEVEL)
+                return false;
+        iterator->index = SHADOW_PT_INDEX(iterator->addr, iterator->level);
+        iterator->sptep = ((u64 *)__va(iterator->shadow_addr)) + iterator->index;
+        return true;
+}
+
+static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
+{
+        iterator->shadow_addr = *iterator->sptep & PT64_BASE_ADDR_MASK;
+        --iterator->level;
+}
+
 static int walk_shadow(struct kvm_shadow_walk *walker,
                        struct kvm_vcpu *vcpu, u64 addr)
 {
-        hpa_t shadow_addr;
-        int level;
+        struct kvm_shadow_walk_iterator iterator;
         int r;
-        u64 *sptep;
-        unsigned index;
-
-        shadow_addr = vcpu->arch.mmu.root_hpa;
-        level = vcpu->arch.mmu.shadow_root_level;
-        if (level == PT32E_ROOT_LEVEL) {
-                shadow_addr = vcpu->arch.mmu.pae_root[(addr >> 30) & 3];
-                shadow_addr &= PT64_BASE_ADDR_MASK;
-                if (!shadow_addr)
-                        return 1;
-                --level;
-        }
 
-        while (level >= PT_PAGE_TABLE_LEVEL) {
-                index = SHADOW_PT_INDEX(addr, level);
-                sptep = ((u64 *)__va(shadow_addr)) + index;
-                r = walker->entry(walker, vcpu, addr, sptep, level);
+        for_each_shadow_entry(vcpu, addr, iterator) {
+                r = walker->entry(walker, vcpu, addr,
+                                  iterator.sptep, iterator.level);
                 if (r)
                         return r;
-                shadow_addr = *sptep & PT64_BASE_ADDR_MASK;
-                --level;
         }
         return 0;
 }