KVM: x86/mmu: Fix TLB flush range when handling disconnected pt

When recursively clearing out disconnected pts, the range based TLB
flush in handle_removed_tdp_mmu_page uses the wrong starting GFN,
resulting in the flush mostly missing the affected range. Fix this by
using base_gfn for the flush.

In response to feedback from David Matlack on the RFC version of this
patch, also move a few definitions into the for loop in the function to
prevent unintended references to them in the future.

Fixes: a066e61f13cf ("KVM: x86/mmu: Factor out handling of removed page tables")
CC: stable@vger.kernel.org
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20211115211704.2621644-1-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index a54c349..377a967 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -317,9 +317,6 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
        struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(pt));
        int level = sp->role.level;
        gfn_t base_gfn = sp->gfn;
-       u64 old_child_spte;
-       u64 *sptep;
-       gfn_t gfn;
        int i;
 
        trace_kvm_mmu_prepare_zap_page(sp);
@@ -327,8 +324,9 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
        tdp_mmu_unlink_page(kvm, sp, shared);
 
        for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
-               sptep = rcu_dereference(pt) + i;
-               gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level);
+               u64 *sptep = rcu_dereference(pt) + i;
+               gfn_t gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level);
+               u64 old_child_spte;
 
                if (shared) {
                        /*
@@ -374,7 +372,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
                                    shared);
        }
 
-       kvm_flush_remote_tlbs_with_address(kvm, gfn,
+       kvm_flush_remote_tlbs_with_address(kvm, base_gfn,
                                           KVM_PAGES_PER_HPAGE(level + 1));
 
        call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);