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  1. 19 2月, 2022 1 次提交
  3. 11 2月, 2022 14 次提交
  5. 20 1月, 2022 1 次提交
  7. 20 12月, 2021 1 次提交
    • S
      KVM: x86: Retry page fault if MMU reload is pending and root has no sp · 18c841e1
      由 Sean Christopherson 提交于 
      Play nice with a NULL shadow page when checking for an obsolete root in
the page fault handler by flagging the page fault as stale if there's no
shadow page associated with the root and KVM_REQ_MMU_RELOAD is pending.
Invalidating memslots, which is the only case where _all_ roots need to
be reloaded, requests all vCPUs to reload their MMUs while holding
mmu_lock for lock.

The "special" roots, e.g. pae_root when KVM uses PAE paging, are not
backed by a shadow page.  Running with TDP disabled or with nested NPT
explodes spectaculary due to dereferencing a NULL shadow page pointer.

Skip the KVM_REQ_MMU_RELOAD check if there is a valid shadow page for the
root.  Zapping shadow pages in response to guest activity, e.g. when the
guest frees a PGD, can trigger KVM_REQ_MMU_RELOAD even if the current
vCPU isn't using the affected root.  I.e. KVM_REQ_MMU_RELOAD can be seen
with a completely valid root shadow page.  This is a bit of a moot point
as KVM currently unloads all roots on KVM_REQ_MMU_RELOAD, but that will
be cleaned up in the future.

Fixes: a955cad8 ("KVM: x86/mmu: Retry page fault if root is invalidated by memslot update")
Cc: stable@vger.kernel.org
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20211209060552.2956723-2-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      18c841e1
  9. 08 12月, 2021 16 次提交
  11. 02 12月, 2021 1 次提交
    • S
      KVM: x86/mmu: Retry page fault if root is invalidated by memslot update · a955cad8
      由 Sean Christopherson 提交于 
      Bail from the page fault handler if the root shadow page was obsoleted by
a memslot update.  Do the check _after_ acuiring mmu_lock, as the TDP MMU
doesn't rely on the memslot/MMU generation, and instead relies on the
root being explicit marked invalid by kvm_mmu_zap_all_fast(), which takes
mmu_lock for write.

For the TDP MMU, inserting a SPTE into an obsolete root can leak a SP if
kvm_tdp_mmu_zap_invalidated_roots() has already zapped the SP, i.e. has
moved past the gfn associated with the SP.

For other MMUs, the resulting behavior is far more convoluted, though
unlikely to be truly problematic.  Installing SPs/SPTEs into the obsolete
root isn't directly problematic, as the obsolete root will be unloaded
and dropped before the vCPU re-enters the guest.  But because the legacy
MMU tracks shadow pages by their role, any SP created by the fault can
can be reused in the new post-reload root.  Again, that _shouldn't_ be
problematic as any leaf child SPTEs will be created for the current/valid
memslot generation, and kvm_mmu_get_page() will not reuse child SPs from
the old generation as they will be flagged as obsolete.  But, given that
continuing with the fault is pointess (the root will be unloaded), apply
the check to all MMUs.

Fixes: b7cccd39 ("KVM: x86/mmu: Fast invalidation for TDP MMU")
Cc: stable@vger.kernel.org
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20211120045046.3940942-5-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      a955cad8
  13. 30 11月, 2021 3 次提交
  15. 26 11月, 2021 3 次提交