[PATCH v2 1/6] KVM: x86/mmu: Fix wrong gfn range of tlb flushing in validate_direct_spte()

Hou Wenlong
2022-08-24T09:29:47Z

The spte pointing to the children SP is dropped, so the
whole gfn range covered by the children SP should be flushed.
Although, Hyper-V may treat a 1-page flush the same if the
address points to a huge page, it still would be better
to use the correct size of huge page. Also introduce
a helper function to do range-based flushing when a direct
SP is dropped, which would help prevent future buggy use
of kvm_flush_remote_tlbs_with_address() in such case.

Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
---
arch/x86/kvm/mmu/mmu.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e418ef3ecfcb..a3578abd8bbc 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -260,6 +260,14 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
kvm_flush_remote_tlbs_with_range(kvm, &range);
}

+/* Flush all memory mapped by the given direct SP. */
+static void kvm_flush_remote_tlbs_direct_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
+{
+ WARN_ON_ONCE(!sp->role.direct);
+ kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
+ KVM_PAGES_PER_HPAGE(sp->role.level + 1));
+}
+
static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
unsigned int access)
{
@@ -2341,7 +2349,7 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
return;

drop_parent_pte(child, sptep);
- kvm_flush_remote_tlbs_with_address(vcpu->kvm, child->gfn, 1);
+ kvm_flush_remote_tlbs_direct_sp(vcpu->kvm, child);
}
}

--
2.31.1