Re: [Bug] x86 EFLAGS refresh is not happening correctly

[Paolo Bonzini]

On 05/08/21 13:24, Paolo Bonzini wrote:
> On 05/08/21 11:51, Stevie Lavern wrote:
> > Shouldn't it be:
> > eflags = cpu_cc_compute_all(env, CC_OP) | (env->df & DF_MASK);
> > as eflags is entirely reevaluated by "cpu_cc_compute_all" ?
>
> No, both are wrong.  env->eflags contains flags other than the 
> arithmetic flags (OF/SF/ZF/AF/PF/CF) and those have to be preserved.
>
> The right code is in helper_read_eflags.  You can move it into 
> cpu_compute_eflags, and make helper_read_eflags use it.

Ah, actually the two are really the same, the TF/VM bits do not apply to 
cpu_compute_eflags so it's correct.

What seems wrong is migration of the EFLAGS register.  There should be 
code in cpu_pre_save and cpu_post_load to special-case it and setup 
CC_DST/CC_OP as done in cpu_load_eflags.

Also, cpu_load_eflags should assert that update_mask does not include 
any of the arithmetic flags.

Paolo