Re: [PATCH] Correct management of REP prefix

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Laurent Vivier wrote:
> This patch corrects some errors appearing when we have an emulation failure
> on an operation using REP prefix.
>
> When x86_emulate_insn() fails, saving EIP and ECX is not enough as emulation
> should have modified other registers like RSI or RDI. Moreover, the emulation
> can fail on the writeback, and in this case we are not able to restore 
> registers.
>
> This patch takes another approach: at the beginning of x86_emulate_insn() we 
> restore state we have at end of x86_decode_insn(). To do that, we store EIP in
> a new field in decode_cache, decode_eip. This field store the EIP as it is at
> the end of x86_decode_insn(); and at beginning of x86_emulate_insn(), we restore
> all registers as they are in vcpu. We can do that, because the x86_decode_insn()
> doesn't modify registers (except EIP).
>   

How about doing it slightly differently: keep c->eip at its current 
meaning, and add c->eip_orig to revert to? That will make the patch 
smaller and reduce the changes of something being missed.


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


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