KVM: x86/mmu: Zap invalidated roots via asynchronous worker

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Use the system worker threads to zap the roots invalidated
by the TDP MMU's "fast zap" mechanism, implemented by
kvm_tdp_mmu_invalidate_all_roots().

At this point, apart from allowing some parallelism in the zapping of
roots, the workqueue is a glorified linked list: work items are added and
flushed entirely within a single kvm->slots_lock critical section.  However,
the workqueue fixes a latent issue where kvm_mmu_zap_all_invalidated_roots()
assumes that it owns a reference to all invalid roots; therefore, no
one can set the invalid bit outside kvm_mmu_zap_all_fast().  Putting the
invalidated roots on a linked list... erm, on a workqueue ensures that
tdp_mmu_zap_root_work() only puts back those extra references that
kvm_mmu_zap_all_invalidated_roots() had gifted to it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Paolo Bonzini 2022-03-02 12:02:07 -05:00

parent bb95dfb9e2

commit 22b94c4b63

4 changed files with 76 additions and 87 deletions

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2

arch/x86/include/asm/kvm_host.h

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5

arch/x86/kvm/mmu/mmu.c

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8

arch/x86/kvm/mmu/mmu_internal.h

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148

arch/x86/kvm/mmu/tdp_mmu.c

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