[PATCH 5.15 072/207] KVM: x86/mmu: Fix TLB flush range when handling disconnected pt

Greg Kroah-Hartman
2021-12-06T15:55:43Z

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);