KVM: MMU: Add rmap_next(), a helper for walking kvm rmaps

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index f52604a7f9e8cd135a964d035cf4c0abda811d21..14e54e331f50a4bc7aef522f7092521f72ba3729 100644 (file)
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -456,28 +456,53 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
        }
 }
 
-static void rmap_write_protect(struct kvm *kvm, u64 gfn)
+static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
 {
        struct kvm_rmap_desc *desc;
+       struct kvm_rmap_desc *prev_desc;
+       u64 *prev_spte;
+       int i;
+
+       if (!*rmapp)
+               return NULL;
+       else if (!(*rmapp & 1)) {
+               if (!spte)
+                       return (u64 *)*rmapp;
+               return NULL;
+       }
+       desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
+       prev_desc = NULL;
+       prev_spte = NULL;
+       while (desc) {
+               for (i = 0; i < RMAP_EXT && desc->shadow_ptes[i]; ++i) {
+                       if (prev_spte == spte)
+                               return desc->shadow_ptes[i];
+                       prev_spte = desc->shadow_ptes[i];
+               }
+               desc = desc->more;
+       }
+       return NULL;
+}
+
+static void rmap_write_protect(struct kvm *kvm, u64 gfn)
+{
        unsigned long *rmapp;
        u64 *spte;
+       u64 *prev_spte;
 
        gfn = unalias_gfn(kvm, gfn);
        rmapp = gfn_to_rmap(kvm, gfn);
 
-       while (*rmapp) {
-               if (!(*rmapp & 1))
-                       spte = (u64 *)*rmapp;
-               else {
-                       desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
-                       spte = desc->shadow_ptes[0];
-               }
+       spte = rmap_next(kvm, rmapp, NULL);
+       while (spte) {
                BUG_ON(!spte);
                BUG_ON(!(*spte & PT_PRESENT_MASK));
                BUG_ON(!(*spte & PT_WRITABLE_MASK));
                rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
-               rmap_remove(kvm, spte);
-               set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
+               prev_spte = spte;
+               spte = rmap_next(kvm, rmapp, spte);
+               rmap_remove(kvm, prev_spte);
+               set_shadow_pte(prev_spte, *prev_spte & ~PT_WRITABLE_MASK);
                kvm_flush_remote_tlbs(kvm);
        }
 }