Re: [RFC PATCH 30/34] accel/tcg: Make tcg-all.c target indpendent

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

On 1/20/24 00:40, Anton Johansson wrote:
> Uses target_supports_mttcg() and target_long_bits() to turn ifdefs into
> runtime branches.
> 
> Signed-off-by: Anton Johansson <anjo@rev.ng>
> ---
>   accel/tcg/tcg-all.c | 25 +++++++++----------------
>   1 file changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
> index a40e0aee37..b8e920e3a8 100644
> --- a/accel/tcg/tcg-all.c
> +++ b/accel/tcg/tcg-all.c
> @@ -28,7 +28,6 @@
>   #include "exec/replay-core.h"
>   #include "sysemu/cpu-timers.h"
>   #include "tcg/tcg.h"
> -#include "tcg/oversized-guest.h"
>   #include "qapi/error.h"
>   #include "qemu/error-report.h"
>   #include "qemu/accel.h"
> @@ -67,20 +66,13 @@ DECLARE_INSTANCE_CHECKER(TCGState, TCG_STATE,
>    * there is one remaining limitation to check:
>    *   - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
>    */
> -
>   static bool default_mttcg_enabled(void)
>   {
> -    if (icount_enabled() || TCG_OVERSIZED_GUEST) {
> +    const bool oversized_guest = target_long_bits() > TCG_TARGET_REG_BITS;
> +    if (icount_enabled() || oversized_guest) {
>           return false;
>       }
> -#ifdef TARGET_SUPPORTS_MTTCG
> -# ifndef TCG_GUEST_DEFAULT_MO
> -#  error "TARGET_SUPPORTS_MTTCG without TCG_GUEST_DEFAULT_MO"
> -# endif
> -    return true;
> -#else
> -    return false;
> -#endif
> +    return target_supports_mttcg();
>   }
>   
>   static void tcg_accel_instance_init(Object *obj)
> @@ -137,17 +129,18 @@ static char *tcg_get_thread(Object *obj, Error **errp)
>   static void tcg_set_thread(Object *obj, const char *value, Error **errp)
>   {
>       TCGState *s = TCG_STATE(obj);
> +    const bool oversized_guest = target_long_bits() > TCG_TARGET_REG_BITS;
>   
>       if (strcmp(value, "multi") == 0) {
> -        if (TCG_OVERSIZED_GUEST) {
> +        if (oversized_guest) {
>               error_setg(errp, "No MTTCG when guest word size > hosts");
>           } else if (icount_enabled()) {
>               error_setg(errp, "No MTTCG when icount is enabled");
>           } else {
> -#ifndef TARGET_SUPPORTS_MTTCG
> -            warn_report("Guest not yet converted to MTTCG - "
> -                        "you may get unexpected results");
> -#endif
> +            if (target_supports_mttcg()) {
> +                warn_report("Guest not yet converted to MTTCG - "
> +                            "you may get unexpected results");
> +            }
>               s->mttcg_enabled = true;
>           }
>       } else if (strcmp(value, "single") == 0) {


All of this happens at startup.  Are you sure you're going to have determined these values 
early enough for heterogeneous mode?  I guess for the moment you don't care, because 
they're all constants supplied by functions.

Acked-by: Richard Henderson <richard.henderson@linaro.org>


r~