• Paolo Bonzini's avatar
    KVM: x86: fix emulation of "movzbl %bpl, %eax" · daf72722
    Paolo Bonzini authored
    When I was looking at RHEL5.9's failure to start with
    unrestricted_guest=0/emulate_invalid_guest_state=1, I got it working with a
    slightly older tree than kvm.git.  I now debugged the remaining failure,
    which was introduced by commit 660696d1 (KVM: X86 emulator: fix
    source operand decoding for 8bit mov[zs]x instructions, 2013-04-24)
    introduced a similar mis-emulation to the one in commit 8acb4207
    fix sil/dil/bpl/spl in the mod/rm fields, 2013-05-30).  The incorrect
    decoding occurs in 8-bit movzx/movsx instructions whose 8-bit operand
    is sil/dil/bpl/spl.
    Needless to say, "movzbl %bpl, %eax" does occur in RHEL5.9's decompression
    prolog, just a handful of instructions before finally giving control to
    the decompressed vmlinux and getting out of the invalid guest state.
    Because OpMem8 bypasses decode_modrm, the same handling of the REX prefix
    must be applied to OpMem8.
    Reported-by: default avatarMichele Baldessari <michele@redhat.com>
    Cc: stable@vger.kernel.org
    Cc: Gleb Natapov <gleb@redhat.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>