[PATCH 1/1] KVM: x86/mmu: Fix TLB flush range when handling disconnected pt

Ben Gardon
2021-11-15T21:42:24Z

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>
---
arch/x86/kvm/mmu/tdp_mmu.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7c5dd83e52de..4bd541050d21 100644
--- 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);
--
2.34.0.rc1.387.gb447b232ab-goog