Commit 614f6970 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86/mmu: do not allow readers to acquire references to invalid roots 



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: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7c554d8e

arch/x86/kvm/mmu/tdp_mmu.c

+5 −4
Original line number Diff line number Diff line
@@ -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);