1. 20 Jun, 2022 1 commit
    • Sean Christopherson's avatar
      KVM: nVMX: Snapshot pre-VM-Enter BNDCFGS for !nested_run_pending case · fa578398
      Sean Christopherson authored
      If a nested run isn't pending, snapshot vmcs01.GUEST_BNDCFGS irrespective
      of whether or not VM_ENTRY_LOAD_BNDCFGS is set in vmcs12.  When restoring
      nested state, e.g. after migration, without a nested run pending,
      prepare_vmcs02() will propagate nested.vmcs01_guest_bndcfgs to vmcs02,
      i.e. will load garbage/zeros into vmcs02.GUEST_BNDCFGS.
      
      If userspace restores nested state before MSRs, then loading garbage is a
      non-issue as loading BNDCFGS will also update vmcs02.  But if usersepace
      restores MSRs first, then KVM is responsible for propagating L2's value,
      which is actually thrown into vmcs01, into vmcs02.
      
      Restoring L2 MSRs into vmcs01, i.e. loading all MSRs before nested state
      is all kinds of bizarre and ideally would not be supported.  Sadly, some
      VMMs do exactly that and rely on KVM to make things work.
      
      Note, there's still a lurking SMM bug, as propagating vmcs01.GUEST_BNDFGS
      to vmcs02 across RSM may corrupt L2's BNDCFGS.  But KVM's entire VMX+SMM
      emulation is flawed as SMI+RSM should not toouch _any_ VMCS when use the
      "default treatment of SMIs", i.e. when not using an SMI Transfer Monitor.
      
      Link: https://lore.kernel.org/all/Yobt1XwOfb5M6Dfa@google.com
      Fixes: 62cf9bd8 ("KVM: nVMX: Fix emulation of VM_ENTRY_LOAD_BNDCFGS")
      Cc: stable@vger.kernel.org
      Cc: Lei Wang <lei4.wang@intel.com>
      Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
      Message-Id: <20220614215831.3762138-2-seanjc@google.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      fa578398
  2. 15 Jun, 2022 13 commits
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  4. 11 Jun, 2022 21 commits