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  1. 11 2月, 2022 12 次提交
  3. 20 1月, 2022 1 次提交
  5. 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
  7. 08 12月, 2021 16 次提交
  9. 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
  11. 30 11月, 2021 3 次提交
  13. 26 11月, 2021 3 次提交
  15. 18 11月, 2021 3 次提交
    • H
      KVM: x86/mmu: Pass parameter flush as false in kvm_tdp_mmu_zap_collapsible_sptes() · 8ed716ca
      由 Hou Wenlong 提交于 
      Since tlb flush has been done for legacy MMU before
kvm_tdp_mmu_zap_collapsible_sptes(), so the parameter flush
should be false for kvm_tdp_mmu_zap_collapsible_sptes().

Fixes: e2209710 ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
Signed-off-by: NHou Wenlong <houwenlong93@linux.alibaba.com>
Message-Id: <21453a1d2533afb6e59fb6c729af89e771ff2e76.1637140154.git.houwenlong93@linux.alibaba.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      8ed716ca
    • H
      KVM: x86/mmu: Skip tlb flush if it has been done in zap_gfn_range() · c7785d85
      由 Hou Wenlong 提交于 
      If the parameter flush is set, zap_gfn_range() would flush remote tlb
when yield, then tlb flush is not needed outside. So use the return
value of zap_gfn_range() directly instead of OR on it in
kvm_unmap_gfn_range() and kvm_tdp_mmu_unmap_gfn_range().

Fixes: 3039bcc7 ("KVM: Move x86's MMU notifier memslot walkers to generic code")
Signed-off-by: NHou Wenlong <houwenlong93@linux.alibaba.com>
Message-Id: <5e16546e228877a4d974f8c0e448a93d52c7a5a9.1637140154.git.houwenlong93@linux.alibaba.com>
Reviewed-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      c7785d85
    • M
      KVM: x86/mmu: include EFER.LMA in extended mmu role · b8453cdc
      由 Maxim Levitsky 提交于 
      Incorporate EFER.LMA into kvm_mmu_extended_role, as it used to compute the
guest root level and is not reflected in kvm_mmu_page_role.level when TDP
is in use.  When simply running the guest, it is impossible for EFER.LMA
and kvm_mmu.root_level to get out of sync, as the guest cannot transition
from PAE paging to 64-bit paging without toggling CR0.PG, i.e. without
first bouncing through a different MMU context.  And stuffing guest state
via KVM_SET_SREGS{,2} also ensures a full MMU context reset.

However, if KVM_SET_SREGS{,2} is followed by KVM_SET_NESTED_STATE, e.g. to
set guest state when migrating the VM while L2 is active, the vCPU state
will reflect L2, not L1.  If L1 is using TDP for L2, then root_mmu will
have been configured using L2's state, despite not being used for L2.  If
L2.EFER.LMA != L1.EFER.LMA, and L2 is using PAE paging, then root_mmu will
be configured for guest PAE paging, but will match the mmu_role for 64-bit
paging and cause KVM to not reconfigure root_mmu on the next nested VM-Exit.

Alternatively, the root_mmu's role could be invalidated after a successful
KVM_SET_NESTED_STATE that yields vcpu->arch.mmu != vcpu->arch.root_mmu,
i.e. that switches the active mmu to guest_mmu, but doing so is unnecessarily
tricky, and not even needed if L1 and L2 do have the same role (e.g., they
are both 64-bit guests and run with the same CR4).
Suggested-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20211115131837.195527-3-mlevitsk@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      b8453cdc