Re: [PATCH] target/i386: fix operand size for VCOMI/VUCOMI instructions

[Peter Maydell]

On Tue, 9 May 2023 at 15:27, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> Compared to other SSE instructions, VUCOMISx and VCOMISx are different:
> the single and double precision versions are distinguished through a
> prefix, however they use no-prefix and 0x66 for SS and SD respectively.
> Scalar values usually are associated with 0xF2 and 0xF3.
>
> Because of these, they incorrectly perform a 128-bit memory load instead
> of a 32- or 64-bit load.  Fix this by writing a custom decoding function.
>
> I tested that the reproducer is fixed and the test-avx output does not
> change.
>
> Reported-by: Gabriele Svelto <gsvelto@mozilla.com>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1637
> Fixes: f8d19eec0d53 ("target/i386: reimplement 0x0f 0x28-0x2f, add AVX", 
> 2022-10-18)
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Worth
Cc: qemu-stable@nongnu.org
also? We have real-world reports of guests falling over on this.

thanks
-- PMM