Commit 16794aaa authored Jan 26, 2015 by Nadav Amit Committed by Paolo Bonzini Jan 26, 2015

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>

parent 2fcf5c8a

arch/x86/kvm/emulate.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -4062,8 +4062,8 @@ static const struct opcode opcode_table[256] = {
		G(ByteOp, group11), G(0, group11),
		/* 0xC8 - 0xCF */
		I(Stack \| SrcImmU16 \| Src2ImmByte, em_enter), I(Stack, em_leave),
		I(ImplicitOps \| Stack \| SrcImmU16, em_ret_far_imm),
		I(ImplicitOps \| Stack, em_ret_far),
		I(ImplicitOps \| SrcImmU16, em_ret_far_imm),
		I(ImplicitOps, em_ret_far),
		D(ImplicitOps), DI(SrcImmByte, intn),
		D(ImplicitOps \| No64), II(ImplicitOps, em_iret, iret),
		/* 0xD0 - 0xD7 */

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