On 4/27/22 17:54, Sasha Levin wrote:
From: Paolo Bonzini pbonzini@redhat.com
[ Upstream commit 614f6970aa70242a3f8a8051b01244c029f77b2a ]
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@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org
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 853780eb033b..7e854313ec3b 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -155,14 +155,15 @@ 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) { \#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)
#define for_each_tdp_mmu_root(_kvm, _root, _as_id) \ list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \ @@ -828,7 +829,7 @@ 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);
Acked-by: Paolo Bonzini pbonzini@redhat.com