[PATCH] KVM: MMU: Implement child shadow unlinking

When removing a page table, we must maintain the parent_pte field all child
shadow page tables.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 38 insertions, 4 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 1484b7211717..7e20dbf4f84c 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -402,12 +402,21 @@ static void mmu_page_remove_parent_pte(struct kvm_mmu_page *page,
                                 break;
                         if (pte_chain->parent_ptes[i] != parent_pte)
                                 continue;
-                        while (i + 1 < NR_PTE_CHAIN_ENTRIES) {
+                        while (i + 1 < NR_PTE_CHAIN_ENTRIES
+                                && pte_chain->parent_ptes[i + 1]) {
                                 pte_chain->parent_ptes[i]
                                         = pte_chain->parent_ptes[i + 1];
                                 ++i;
                         }
                         pte_chain->parent_ptes[i] = NULL;
+                        if (i == 0) {
+                                hlist_del(&pte_chain->link);
+                                kfree(pte_chain);
+                                if (hlist_empty(&page->parent_ptes)) {
+                                        page->multimapped = 0;
+                                        page->parent_pte = NULL;
+                                }
+                        }
                         return;
                 }
         BUG();
@@ -481,7 +490,30 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 static void kvm_mmu_page_unlink_children(struct kvm_vcpu *vcpu,
                                          struct kvm_mmu_page *page)
 {
-        BUG();
+        unsigned i;
+        u64 *pt;
+        u64 ent;
+
+        pt = __va(page->page_hpa);
+
+        if (page->role.level == PT_PAGE_TABLE_LEVEL) {
+                for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+                        if (pt[i] & PT_PRESENT_MASK)
+                                rmap_remove(vcpu->kvm, &pt[i]);
+                        pt[i] = 0;
+                }
+                return;
+        }
+
+        for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+                ent = pt[i];
+
+                pt[i] = 0;
+                if (!(ent & PT_PRESENT_MASK))
+                        continue;
+                ent &= PT64_BASE_ADDR_MASK;
+                mmu_page_remove_parent_pte(page_header(ent), &pt[i]);
+        }
 }
 
 static void kvm_mmu_put_page(struct kvm_vcpu *vcpu,
@@ -489,8 +521,7 @@ static void kvm_mmu_put_page(struct kvm_vcpu *vcpu,
                              u64 *parent_pte)
 {
         mmu_page_remove_parent_pte(page, parent_pte);
-        if (page->role.level > PT_PAGE_TABLE_LEVEL)
-                kvm_mmu_page_unlink_children(vcpu, page);
+        kvm_mmu_page_unlink_children(vcpu, page);
         hlist_del(&page->hash_link);
         list_del(&page->link);
         list_add(&page->link, &vcpu->free_pages);
@@ -511,6 +542,7 @@ static void kvm_mmu_zap_page(struct kvm_vcpu *vcpu,
                                              struct kvm_pte_chain, link);
                         parent_pte = chain->parent_ptes[0];
                 }
+                BUG_ON(!parent_pte);
                 kvm_mmu_put_page(vcpu, page, parent_pte);
                 *parent_pte = 0;
         }
@@ -530,6 +562,8 @@ static int kvm_mmu_unprotect_page(struct kvm_vcpu *vcpu, gfn_t gfn)
         bucket = &vcpu->kvm->mmu_page_hash[index];
         hlist_for_each_entry_safe(page, node, n, bucket, hash_link)
                 if (page->gfn == gfn && !page->role.metaphysical) {
+                        pgprintk("%s: gfn %lx role %x\n", __FUNCTION__, gfn,
+                                 page->role.word);
                         kvm_mmu_zap_page(vcpu, page);
                         r = 1;
                 }