[PATCH] target/ppc: Better CTRL SPR implementation

[PATCH] target/ppc: Better CTRL SPR implementation

[Nicholas Piggin]

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>
---
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,
-- 
2.40.1

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

[Cédric Le Goater]

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,