Avi Kivity wrote: > 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.
I didn't do like that because I was afraid to miss some points to restore
orig_eip.
But a patch will follow...
Laurent
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