Re: [PATCH 01/18] target/i386/tcg: fix check for invalid VSIB instruction

[Richard Henderson <richard.henderson@linaro.org>]

On 12/10/25 07:16, Paolo Bonzini wrote:
> VSIB instructions (VEX class 12) must not have an address prefix.
> Checking s->aflag == MO_16 is not enough because in 64-bit mode
> the address prefix changes aflag to MO_32.  Add a specific check
> bit instead.
> 
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   target/i386/tcg/decode-new.h     |  3 +++
>   target/i386/tcg/decode-new.c.inc | 27 +++++++++++++--------------
>   2 files changed, 16 insertions(+), 14 deletions(-)

Where do you see this?  I think this is wrong.

In particular,

Table 2-27. Type 12 Class Exception Conditions
- If address size attribute is 16 bit.

and

2.3.12 Vector SIB (VSIB) Memory Addressing
In 16-bit protected mode, VSIB memory addressing is permitted if address size attribute is 
overridden to 32 bits.

Therefore, in 16-bit mode, one *must* use the address prefix.



r~