[ 004/102] KVM: emulator: emulate SALC

From: Greg Kroah-Hartman
Date: Fri May 17 2013 - 18:27:35 EST

3.9-stable review patch. If anyone has any objections, please let me know.


From: Paolo Bonzini <pbonzini@xxxxxxxxxx>

commit 326f578f7e1443bac2333712dd130a261ec15288 upstream.

This is an almost-undocumented instruction available in 32-bit mode.
I say "almost" undocumented because AMD documents it in their opcode
maps just to say that it is unavailable in 64-bit mode (sections
"A.2.1 One-Byte Opcodes" and "B.3 Invalid and Reassigned Instructions
in 64-Bit Mode").

It is roughly equivalent to "sbb %al, %al" except it does not
set the flags. Use fastop to emulate it, but do not use the opcode
directly because it would fail if the host is 64-bit!

Reported-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/kvm/emulate.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -534,6 +534,9 @@ FOP_SETCC(setle)

+FOP_START(salc) "pushf; sbb %al, %al; popf \n\t" FOP_RET
#define __emulate_1op_rax_rdx(ctxt, _op, _suffix, _ex) \
do { \
unsigned long _tmp; \
@@ -3951,7 +3954,8 @@ static const struct opcode opcode_table[
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,
+ I(DstAcc | SrcImmUByte | No64, em_aad),
+ F(DstAcc | ByteOp | No64, em_salc),
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,

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/