Remove the "shared" argument of for_each_tdp_mmu_root_yield_safe, thus ensuring
that readers do not ever acquire a reference to an invalid root. After this
patch, all readers except kvm_tdp_mmu_zap_invalidated_roots() treat
refcount=0/valid, refcount=0/invalid and refcount=1/invalid in exactly the
same way. kvm_tdp_mmu_zap_invalidated_roots() is different but it also
does not acquire a reference to the invalid root, and it cannot see
refcount=0/invalid because it is guaranteed to run after
kvm_tdp_mmu_invalidate_all_roots().
Opportunistically add a lockdep assertion to the yield-safe iterator.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index d39593b9ac9e..79bc48ddb69d 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -166,14 +166,15 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _only_valid); \
_root; \
_root = tdp_mmu_next_root(_kvm, _root, _shared, _only_valid)) \
- if (kvm_mmu_page_as_id(_root) != _as_id) { \
+ if (kvm_lockdep_assert_mmu_lock_held(_kvm, _shared) && \
+ kvm_mmu_page_as_id(_root) != _as_id) { \
} else
#define for_each_valid_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
__for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, true)
-#define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
- __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, false)
+#define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id) \
+ __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, false, false)
/*
* Iterate over all TDP MMU roots. Requires that mmu_lock be held for write,
@@ -808,7 +809,7 @@ bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start,
{
struct kvm_mmu_page *root;
- for_each_tdp_mmu_root_yield_safe(kvm, root, as_id, false)
+ for_each_tdp_mmu_root_yield_safe(kvm, root, as_id)
flush = zap_gfn_range(kvm, root, start, end, can_yield, flush,
false);
--
2.31.1
