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Commit b5bbf10e authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: Emulation of MOV-sreg to memory uses incorrect size 



In x86, you can only MOV-sreg to memory with either 16-bits or 64-bits size.
In contrast, KVM may write to 32-bits memory on MOV-sreg. This patch fixes KVM
behavior, and sets the destination operand size to two, if the destination is
memory.

When destination is registers, and the operand size is 32-bits, the high
16-bits in modern CPUs is filled with zero.  This is handled correctly.

Signed-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 82b32774

arch/x86/kvm/emulate.c

+2 −0
Original line number Diff line number Diff line
@@ -3207,6 +3207,8 @@ static int em_mov_rm_sreg(struct x86_emulate_ctxt *ctxt) 
		return emulate_ud(ctxt);



	ctxt->dst.val = get_segment_selector(ctxt, ctxt->modrm_reg);

	if (ctxt->dst.bytes == 4 && ctxt->dst.type == OP_MEM)

		ctxt->dst.bytes = 2;

	return X86EMUL_CONTINUE;

}