KVM: MMU: Don't flush shadow when enabling dirty tracking

Instead, drop large mappings, which were the reason we dropped shadow.

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

2 files changed, 9 insertions, 10 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f02b8edc3d44..ccacf0b1b540 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3538,14 +3538,18 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
                 if (!test_bit(slot, sp->slot_bitmap))
                         continue;
 
-                if (sp->role.level != PT_PAGE_TABLE_LEVEL)
-                        continue;
-
                 pt = sp->spt;
-                for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
+                for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+                        if (sp->role.level != PT_PAGE_TABLE_LEVEL
+                            && is_large_pte(pt[i])) {
+                                drop_spte(kvm, &pt[i],
+                                          shadow_trap_nonpresent_pte);
+                                --kvm->stat.lpages;
+                        }
                         /* avoid RMW */
                         if (is_writable_pte(pt[i]))
                                 update_spte(&pt[i], pt[i] & ~PT_WRITABLE_MASK);
+                }
         }
         kvm_flush_remote_tlbs(kvm);
 }
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f29abeb6a912..a3a8f5fb369e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -621,7 +621,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
                             struct kvm_userspace_memory_region *mem,
                             int user_alloc)
 {
-        int r, flush_shadow = 0;
+        int r;
         gfn_t base_gfn;
         unsigned long npages;
         unsigned long i;
@@ -741,8 +741,6 @@ skip_lpage:
                 if (kvm_create_dirty_bitmap(&new) < 0)
                         goto out_free;
                 /* destroy any largepage mappings for dirty tracking */
-                if (old.npages)
-                        flush_shadow = 1;
         }
 #else  /* not defined CONFIG_S390 */
         new.user_alloc = user_alloc;
@@ -813,9 +811,6 @@ skip_lpage:
         kvm_free_physmem_slot(&old, &new);
         kfree(old_memslots);
 
-        if (flush_shadow)
-                kvm_arch_flush_shadow(kvm);
-
         return 0;
 
 out_free: