Messages in this thread | | | Date | Wed, 27 Apr 2022 18:20:32 +0200 | Subject | Re: [PATCH MANUALSEL 5.15 4/7] KVM: x86/mmu: do not allow readers to acquire references to invalid roots | From | Paolo Bonzini <> |
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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) { \ > } 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) > > #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); >
Sorry no, this is a NACK.
Paolo
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