[PATCH 1/5] KVM: MMU: Add for_each_shadow_entry(), a simpler alternative to walk_shadow()

[Avi Kivity]

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 <a...@redhat.com>
---
 arch/x86/kvm/mmu.c |   69 +++++++++++++++++++++++++++++++++++++---------------
 1 files changed, 49 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3b86df6..3248a3e 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;
 }
-- 
1.6.0.6

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