KVM: x86/mmu: Process only valid TDP MMU roots when aging a gfn range

Skip invalid TDP MMU roots when aging a gfn range.  There is zero reason
to process invalid roots, as they by definition hold stale information.
E.g. if a root is invalid because its from a previous memslot generation,
in the unlikely event the root has a SPTE for the gfn, then odds are good
that the gfn=>hva mapping is different, i.e. doesn't map to the hva that
is being aged by the primary MMU.

Link: https://lore.kernel.org/r/20241011021051.1557902-14-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 f77927b57962b900e4687d173e169cdcec10e9fd..e8c061bf94ec81291c8970078269646795432464 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1205,9 +1205,11 @@ static __always_inline bool kvm_tdp_mmu_handle_gfn(struct kvm *kvm,
 
        /*
         * Don't support rescheduling, none of the MMU notifiers that funnel
-        * into this helper allow blocking; it'd be dead, wasteful code.
+        * into this helper allow blocking; it'd be dead, wasteful code.  Note,
+        * this helper must NOT be used to unmap GFNs, as it processes only
+        * valid roots!
         */
-       for_each_tdp_mmu_root(kvm, root, range->slot->as_id) {
+       for_each_valid_tdp_mmu_root(kvm, root, range->slot->as_id) {
                rcu_read_lock();
 
                tdp_root_for_each_leaf_pte(iter, root, range->start, range->end)