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KVM: x86: Wrong operand size for far ret 

Indeed, Intel SDM specifically states that for the RET instruction "In 64-bit
mode, the default operation size of this instruction is the stack-address size,
i.e. 64 bits."

However, experiments show this is not the case. Here is for example objdump of
small 64-bit asm:

  4004f1:	ca 14 00             	lret   $0x14
  4004f4:	48 cb                	lretq
  4004f6:	48 ca 14 00          	lretq  $0x14

Therefore, remove the Stack flag from far-ret instructions.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2015-01-26 09:32:22 +02:00 committed by Paolo Bonzini
parent 2fcf5c8ae2
commit 16794aaaab
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kvm/emulate.c
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@ -4062,8 +4062,8 @@ static const struct opcode opcode_table[256] = {
G(ByteOp, group11), G(0, group11), G(ByteOp, group11), G(0, group11),
/* 0xC8 - 0xCF */ /* 0xC8 - 0xCF */
I(Stack | SrcImmU16 | Src2ImmByte, em_enter), I(Stack, em_leave), I(Stack | SrcImmU16 | Src2ImmByte, em_enter), I(Stack, em_leave),
I(ImplicitOps | Stack | SrcImmU16, em_ret_far_imm), I(ImplicitOps | SrcImmU16, em_ret_far_imm),
I(ImplicitOps | Stack, em_ret_far), I(ImplicitOps, em_ret_far),
D(ImplicitOps), DI(SrcImmByte, intn), D(ImplicitOps), DI(SrcImmByte, intn),
D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret), D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret),
/* 0xD0 - 0xD7 */ /* 0xD0 - 0xD7 */