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    Subject[PATCH 5.15 072/207] KVM: x86/mmu: Fix TLB flush range when handling disconnected pt
    Date
    From: Ben Gardon <bgardon@google.com>

    commit 574c3c55e969096cea770eda3375ff35ccf91702 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kvm/mmu/tdp_mmu.c | 10 ++++------
    1 file changed, 4 insertions(+), 6 deletions(-)

    --- a/arch/x86/kvm/mmu/tdp_mmu.c
    +++ b/arch/x86/kvm/mmu/tdp_mmu.c
    @@ -316,9 +316,6 @@ static void handle_removed_tdp_mmu_page(
    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);
    @@ -326,8 +323,9 @@ static void handle_removed_tdp_mmu_page(
    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) {
    /*
    @@ -373,7 +371,7 @@ static void handle_removed_tdp_mmu_page(
    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);

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