Re: [kvm-unit-tests PATCH v3 1/2] x86: realmode: save and restore %es

[Jim Mattson <jmattson@xxxxxxxxxx>]

On Mon, Nov 4, 2019 at 4:08 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 01/11/19 21:33, Bill Wendling wrote:
> > Some of the code test sequences (e.g. push_es) clobber ES. That causes
> > trouble for future rep string instructions. So save and restore ES
> > around the test code sequence in exec_in_big_real_mode.
>
> You mean pop_es.  Applied with that change.

I think push_es and pop_es are both guilty of clobbering %es:

MK_INSN(push_es, "mov $0x231, %bx\n\t" //Just write a dummy value to
see if it gets overwritten
"mov $0x123, %ax\n\t"
"mov %ax, %es\n\t"   <======= Here
"push %es\n\t"
"pop %bx \n\t"
);

MK_INSN(pop_es, "push %ax\n\t"
"pop %es\n\t"          <======== Here
"mov %es, %bx\n\t"
);