Re: [PATCH] target/i386: implement undocumented "smsw r32" behavior

[Roman Bolshakov <r.bolshakov@yadro.com>]

On Fri, Jun 26, 2020 at 06:44:19AM -0400, Paolo Bonzini wrote:
> In 32-bit mode, the higher 16 bits of the destination
> register are undefined.  In practice CR0[31:0] is stored,
> just like in 64-bit mode, so just remove the "if" that
> currently differentiates the behavior.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Hi Paolo,

It seems to be a follow-up to the kvm-unit-tests patch:
https://patchwork.kernel.org/patch/11590445/

Could you please add:
Reported-by: Roman Bolshakov <r.bolshakov@yadro.com>

> ---
>  target/i386/translate.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/target/i386/translate.c b/target/i386/translate.c
> index 4d808a6f93..60eac03498 100644
> --- a/target/i386/translate.c
> +++ b/target/i386/translate.c
> @@ -7579,12 +7579,13 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
>          CASE_MODRM_OP(4): /* smsw */
>              gen_svm_check_intercept(s, pc_start, SVM_EXIT_READ_CR0);
>              tcg_gen_ld_tl(s->T0, cpu_env, offsetof(CPUX86State, cr[0]));
> -            if (CODE64(s)) {
> -                mod = (modrm >> 6) & 3;
> -                ot = (mod != 3 ? MO_16 : s->dflag);
> -            } else {
> -                ot = MO_16;
> -            }
> +            /*
> +             * In 32-bit mode, the higher 16 bits of the destination
> +             * register are undefined.  In practice CR0[31:0] is stored
> +             * just like in 64-bit mode.
> +             */
> +            mod = (modrm >> 6) & 3;
> +            ot = (mod != 3 ? MO_16 : s->dflag);
>              gen_ldst_modrm(env, s, modrm, ot, OR_TMP0, 1);
>              break;
>          case 0xee: /* rdpkru */
> -- 
> 2.26.2
> 
> 

Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>

Regards,
Roman