• Sean Christopherson's avatar
    KVM: nVMX: Consult only the "basic" exit reason when routing nested exit · 2ebac8bb
    Sean Christopherson authored
    Consult only the basic exit reason, i.e. bits 15:0 of vmcs.EXIT_REASON,
    when determining whether a nested VM-Exit should be reflected into L1 or
    handled by KVM in L0.
    
    For better or worse, the switch statement in nested_vmx_exit_reflected()
    currently defaults to "true", i.e. reflects any nested VM-Exit without
    dedicated logic.  Because the case statements only contain the basic
    exit reason, any VM-Exit with modifier bits set will be reflected to L1,
    even if KVM intended to handle it in L0.
    
    Practically speaking, this only affects EXIT_REASON_MCE_DURING_VMENTRY,
    i.e. a #MC that occurs on nested VM-Enter would be incorrectly routed to
    L1, as "failed VM-Entry" is the only modifier that KVM can currently
    encounter.  The SMM modifiers will never be generated as KVM doesn't
    support/employ a SMI Transfer Monitor.  Ditto for "exit from enclave",
    as KVM doesn't yet support virtualizing SGX, i.e. it's impossible to
    enter an enclave in a KVM guest (L1 or L2).
    
    Fixes: 644d711a ("KVM: nVMX: Deciding if L0 or L1 should handle an L2 exit")
    Cc: Jim Mattson <jmattson@google.com>
    Cc: Xiaoyao Li <xiaoyao.li@intel.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
    Message-Id: <20200227174430.26371-1-sean.j.christopherson@intel.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    2ebac8bb
nested.c 192 KB