[PATCH 0/4] KVM: x86/mmu: Zap invalid TDP MMU roots when unmapping

[Sean Christopherson]

Patches 01-03 implement a bug fix by ensuring KVM zaps both valid and
invalid roots when unmapping a gfn range (including the magic "all" range).
Failure to zap invalid roots means KVM doesn't honor the mmu_notifier's
requirement that all references are dropped.

set_nx_huge_pages() is the most blatant offender, as it doesn't elevate
mm_users and so a VM's entire mm can be released, but the same underlying
bug exists for any "unmap" command from the mmu_notifier in combination
with a memslot update.  E.g. if KVM is deleting a memslot, and a
mmu_notifier hook acquires mmu_lock while it's dropped by
kvm_mmu_zap_all_fast(), the mmu_notifier hook will see the to-be-deleted
memslot but won't zap entries from the invalid roots.

Patch 04 is cleanup to reuse the common iterator for walking _only_
invalid roots.

Sean Christopherson (4):
  KVM: x86/mmu: Use common TDP MMU zap helper for MMU notifier unmap
    hook
  KVM: x86/mmu: Move "invalid" check out of kvm_tdp_mmu_get_root()
  KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU
  KVM: x86/mmu: Use common iterator for walking invalid TDP MMU roots

 arch/x86/kvm/mmu/tdp_mmu.c | 116 +++++++++++++++++--------------------
 arch/x86/kvm/mmu/tdp_mmu.h |   3 -
 2 files changed, 53 insertions(+), 66 deletions(-)

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2.34.1.173.g76aa8bc2d0-goog