Re: [PATCH] x86 emulator: Update EIP even with instructions with no writeback

[Avi Kivity <avi@qumranet.com>]

Mohammed Gamal wrote:
> This patch resolves the problem encountered with HLT emulation with FreeDOS's HIMEM XMS Driver. 
>
> HLT is the only instruction that goes to the done label unconditionally, 
> causing the EIP value not to be updated which leads to the guest looping
> forever on the same instruction.
>
> Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
>
> ---
>
>  arch/x86/kvm/x86_emulate.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
> index dd4efe1..04d7f02 100644
> --- a/arch/x86/kvm/x86_emulate.c
> +++ b/arch/x86/kvm/x86_emulate.c
> @@ -1769,13 +1769,15 @@ writeback:
>  
>  	/* Commit shadow register state. */
>  	memcpy(ctxt->vcpu->arch.regs, c->regs, sizeof c->regs);
> -	kvm_rip_write(ctxt->vcpu, c->eip);
>  
>  done:
>  	if (rc == X86EMUL_UNHANDLEABLE) {
>  		c->eip = saved_eip;
>  		return -1;
>  	}
> +	else
> +		kvm_rip_write(ctxt->vcpu, c->eip);
> +
>  	return 0;

Why not change hlt to writeback like all other instructions?

-- 
error compiling committee.c: too many arguments to function