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

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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>

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Paolo Bonzini 2022-03-02 08:51:05 -05:00

parent 7c554d8e51

commit 614f6970aa

1 changed files with 5 additions and 4 deletions

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arch/x86/kvm/mmu/tdp_mmu.c

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