Re: [PATCH] target/ppc: Better CTRL SPR implementation

["Cédric Le Goater" <clegoate@redhat.com>]

On 6/20/23 15:15, Nicholas Piggin wrote:
> The CTRL register is able to write the bit in the RUN field, which gets
> reflected into the TS field which is read-only and contains the state of
> the RUN field for all threads in the core.
> 
> TCG does not implement SMT, so the correct implementation just requires
> mirroring the RUN bit into the first bit of the TS field.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>


Applied to ppc-next.

Thanks,

C.



> ---
> This is also unchanged from last posting except improved changelog.
> The pseries TCG SMT patches depend on this one, but it is good to go
> by itself too (this is what CTRL appears like to hardware KVM guest).
> 
> Thanks,
> Nick
> 
>   target/ppc/translate.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index b591f2e496..1ade063616 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -418,7 +418,14 @@ void spr_write_generic32(DisasContext *ctx, int sprn, int gprn)
>   
>   void spr_write_CTRL(DisasContext *ctx, int sprn, int gprn)
>   {
> -    spr_write_generic32(ctx, sprn, gprn);
> +    /* This does not implement >1 thread */
> +    TCGv t0 = tcg_temp_new();
> +    TCGv t1 = tcg_temp_new();
> +    tcg_gen_extract_tl(t0, cpu_gpr[gprn], 0, 1); /* Extract RUN field */
> +    tcg_gen_shli_tl(t1, t0, 8); /* Duplicate the bit in TS */
> +    tcg_gen_or_tl(t1, t1, t0);
> +    gen_store_spr(sprn, t1);
> +    spr_store_dump_spr(sprn);
>   
>       /*
>        * SPR_CTRL writes must force a new translation block,