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    SubjectRe: [PATCH v2 2/3] KVM: emulator: emulate XLAT
    On Thu, May 09, 2013 at 11:32:50AM +0200, Paolo Bonzini wrote:
    > This is used by SGABIOS, KVM breaks with emulate_invalid_guest_state=1.
    > It is just a MOV in disguise, with a funny source address.
    >
    > Reported-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
    > Cc: stable@vger.kernel.org # 3.9
    > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    > ---
    > arch/x86/kvm/emulate.c | 16 +++++++++++++++-
    > 1 file changed, 15 insertions(+), 1 deletion(-)
    >
    > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
    > index 709ba03..210bb4e 100644
    > --- a/arch/x86/kvm/emulate.c
    > +++ b/arch/x86/kvm/emulate.c
    > @@ -60,6 +60,7 @@
    > #define OpGS 25ull /* GS */
    > #define OpMem8 26ull /* 8-bit zero extended memory operand */
    > #define OpImm64 27ull /* Sign extended 16/32/64-bit immediate */
    > +#define OpXLat 28ull /* memory at BX/EBX/RBX + zero-extended AL */
    >
    > #define OpBits 5 /* Width of operand field */
    > #define OpMask ((1ull << OpBits) - 1)
    > @@ -99,6 +100,7 @@
    > #define SrcImmUByte (OpImmUByte << SrcShift)
    > #define SrcImmU (OpImmU << SrcShift)
    > #define SrcSI (OpSI << SrcShift)
    > +#define SrcXLat (OpXLat << SrcShift)
    > #define SrcImmFAddr (OpImmFAddr << SrcShift)
    > #define SrcMemFAddr (OpMemFAddr << SrcShift)
    > #define SrcAcc (OpAcc << SrcShift)
    > @@ -3949,7 +3951,8 @@ static const struct opcode opcode_table[256] = {
    > G(Src2One | ByteOp, group2), G(Src2One, group2),
    > G(Src2CL | ByteOp, group2), G(Src2CL, group2),
    > I(DstAcc | SrcImmUByte | No64, em_aam),
    > - I(DstAcc | SrcImmUByte | No64, em_aad), N, N,
    > + I(DstAcc | SrcImmUByte | No64, em_aad), N,
    > + I(DstAcc | SrcXLat | ByteOp, em_mov),
    > /* 0xD8 - 0xDF */
    > N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,
    > /* 0xE0 - 0xE7 */
    > @@ -4207,6 +4210,17 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
    > op->val = 0;
    > op->count = 1;
    > break;
    > + case OpXLat:
    Sigh, obviously this is not reusable by any other instruction. So many
    waisted transistor :(

    > + op->type = OP_MEM;
    > + op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
    > + op->addr.mem.ea =
    > + register_address(ctxt,
    > + reg_read(ctxt, VCPU_REGS_RBX) +
    > + (reg_read(ctxt, VCPU_REGS_RAX) & 0xff));
    > + op->addr.mem.seg = seg_override(ctxt);
    > + op->val = 0;
    > + op->count = 1;
    The count is set only for decoding that is used by string instructions.
    I can drop it while applying.

    > + break;
    > case OpImmFAddr:
    > op->type = OP_IMM;
    > op->addr.mem.ea = ctxt->_eip;
    > --
    > 1.8.1.4
    >

    --
    Gleb.


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