KVM: x86/mmu: Consolidate Dirty vs. Writable clearing logic in TDP MMU

Deduplicate the guts of the TDP MMU's clearing of dirty status by
snapshotting whether to check+clear the Dirty bit vs. the Writable bit,
which is the only difference between the two flavors of dirty tracking.

Note, kvm_ad_enabled() is just a wrapper for shadow_accessed_mask, i.e.
is constant after kvm-{intel,amd}.ko is loaded.

Link: https://lore.kernel.org/all/Yz4Qi7cn7TWTWQjj@google.com
Signed-off-by: Vipin Sharma <vipinsh@google.com>
[sean: split to separate patch, apply to dirty log, write changelog]
Link: https://lore.kernel.org/r/20230321220021.2119033-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 5a56426..b32c9ba 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1607,8 +1607,8 @@ void kvm_tdp_mmu_try_split_huge_pages(struct kvm *kvm,
 static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
                           gfn_t start, gfn_t end)
 {
+       u64 dbit = kvm_ad_enabled() ? shadow_dirty_mask : PT_WRITABLE_MASK;
        struct tdp_iter iter;
-       u64 new_spte;
        bool spte_set = false;
 
        rcu_read_lock();
@@ -1624,19 +1624,10 @@ retry:
                MMU_WARN_ON(kvm_ad_enabled() &&
                            spte_ad_need_write_protect(iter.old_spte));
 
-               if (!kvm_ad_enabled()) {
-                       if (is_writable_pte(iter.old_spte))
-                               new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
-                       else
-                               continue;
-               } else {
-                       if (iter.old_spte & shadow_dirty_mask)
-                               new_spte = iter.old_spte & ~shadow_dirty_mask;
-                       else
-                               continue;
-               }
+               if (!(iter.old_spte & dbit))
+                       continue;
 
-               if (tdp_mmu_set_spte_atomic(kvm, &iter, new_spte))
+               if (tdp_mmu_set_spte_atomic(kvm, &iter, iter.old_spte & ~dbit))
                        goto retry;
 
                spte_set = true;
@@ -1678,8 +1669,9 @@ bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
 static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root,
                                  gfn_t gfn, unsigned long mask, bool wrprot)
 {
+       u64 dbit = (wrprot || !kvm_ad_enabled()) ? PT_WRITABLE_MASK :
+                                                  shadow_dirty_mask;
        struct tdp_iter iter;
-       u64 new_spte;
 
        rcu_read_lock();
 
@@ -1697,19 +1689,10 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root,
 
                mask &= ~(1UL << (iter.gfn - gfn));
 
-               if (wrprot || !kvm_ad_enabled()) {
-                       if (is_writable_pte(iter.old_spte))
-                               new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
-                       else
-                               continue;
-               } else {
-                       if (iter.old_spte & shadow_dirty_mask)
-                               new_spte = iter.old_spte & ~shadow_dirty_mask;
-                       else
-                               continue;
-               }
+               if (!(iter.old_spte & dbit))
+                       continue;
 
-               tdp_mmu_set_spte_no_dirty_log(kvm, &iter, new_spte);
+               tdp_mmu_set_spte_no_dirty_log(kvm, &iter, iter.old_spte & ~dbit);
        }
 
        rcu_read_unlock();