KVM: MMU: Split the main body of rmap_write_protect() off from others

We will use this in the following patch to implement another function
which needs to write protect pages using the rmap information.

Note that there is a small change in debug printing for large pages:
we do not differentiate them from others to avoid duplicating code.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 27 insertions, 26 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4cb164268846..c8b5694d1a48 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1010,42 +1010,43 @@ static void drop_spte(struct kvm *kvm, u64 *sptep)
                 rmap_remove(kvm, sptep);
 }
 
-int kvm_mmu_rmap_write_protect(struct kvm *kvm, u64 gfn,
-                               struct kvm_memory_slot *slot)
+static int __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level)
 {
-        unsigned long *rmapp;
-        u64 *spte;
-        int i, write_protected = 0;
+        u64 *spte = NULL;
+        int write_protected = 0;
 
-        rmapp = __gfn_to_rmap(gfn, PT_PAGE_TABLE_LEVEL, slot);
-        spte = rmap_next(rmapp, NULL);
-        while (spte) {
+        while ((spte = rmap_next(rmapp, spte))) {
                 BUG_ON(!(*spte & PT_PRESENT_MASK));
                 rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
-                if (is_writable_pte(*spte)) {
+
+                if (!is_writable_pte(*spte))
+                        continue;
+
+                if (level == PT_PAGE_TABLE_LEVEL) {
                         mmu_spte_update(spte, *spte & ~PT_WRITABLE_MASK);
-                        write_protected = 1;
+                } else {
+                        BUG_ON(!is_large_pte(*spte));
+                        drop_spte(kvm, spte);
+                        --kvm->stat.lpages;
+                        spte = NULL;
                 }
-                spte = rmap_next(rmapp, spte);
+
+                write_protected = 1;
         }
 
-        /* check for huge page mappings */
-        for (i = PT_DIRECTORY_LEVEL;
+        return write_protected;
+}
+
+int kvm_mmu_rmap_write_protect(struct kvm *kvm, u64 gfn,
+                               struct kvm_memory_slot *slot)
+{
+        unsigned long *rmapp;
+        int i, write_protected = 0;
+
+        for (i = PT_PAGE_TABLE_LEVEL;
              i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
                 rmapp = __gfn_to_rmap(gfn, i, slot);
-                spte = rmap_next(rmapp, NULL);
-                while (spte) {
-                        BUG_ON(!(*spte & PT_PRESENT_MASK));
-                        BUG_ON(!is_large_pte(*spte));
-                        pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);
-                        if (is_writable_pte(*spte)) {
-                                drop_spte(kvm, spte);
-                                --kvm->stat.lpages;
-                                spte = NULL;
-                                write_protected = 1;
-                        }
-                        spte = rmap_next(rmapp, spte);
-                }
+                write_protected |= __rmap_write_protect(kvm, rmapp, i);
         }
 
         return write_protected;