kvm mmu uses "if (is_tdp_mmu(vcpu->arch.mmu))" to choose between tdp mmu
and shadow path.
If a root is a tdp mmu page while its root_count is 0, it's not valid to
go to the shadow path.
So, return true and add a warn on zero root count.
Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index c163f7cc23ca..58b4881654a9 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -74,6 +74,7 @@ static inline bool is_tdp_mmu(struct kvm_mmu *mmu)
{
struct kvm_mmu_page *sp;
hpa_t hpa = mmu->root.hpa;
+ bool is_tdp;
if (WARN_ON(!VALID_PAGE(hpa)))
return false;
@@ -84,7 +85,10 @@ static inline bool is_tdp_mmu(struct kvm_mmu *mmu)
* pae_root page, not a shadow page.
*/
sp = to_shadow_page(hpa);
- return sp && is_tdp_mmu_page(sp) && sp->root_count;
+ is_tdp = sp && is_tdp_mmu_page(sp);
+ WARN_ON(is_tdp && !refcount_read(&sp->tdp_mmu_root_count));
+
+ return is_tdp;
}
#else
static inline int kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return 0; }
--
2.17.1
