Re: Bug: fstenv is wrongly implemented

[Peter Maydell]

On Fri, 2 Apr 2021 at 09:47, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 02/04/21 10:29, Ziqiao Kong wrote:
> >
> > According to git blame, this bug is introduced about 13 years ago:
> > https://github.com/qemu/qemu/blame/633decd71119a4293e5e53e6059026c517a8bef0/target-i386/fpu_helper.c#L997.
> >
> > We also had a patch for this bug:
> > https://github.com/unicorn-engine/unicorn/commit/59b09a71bfc6fd8b95357944f6be9aa54f424421
> > which you may refer to. I can also help draft a patch if necessary.
>
> Hi!
>
> Unfortunately the patch is incorrect, because fpu_update_ip is called
> only at translation time and not at run-time.  If more than one x87
> instruction is present in the same translation block, or if a
> translation block has been compiled after the one that is executing,
> env->fpip will be incorrect.

I think this is https://bugs.launchpad.net/qemu/+bug/661696 ?
That had a patch attached which got some on-list discussion
back in 2010:
https://lists.gnu.org/archive/html/qemu-devel/2010-11/msg02497.html
The review comments may be of help in coming up with an updated patch.

thanks
-- PMM