Re: [PATCH 4/8] accel/tcg: Add guest_base_signed_addr32 for user-only

[Philippe Mathieu-Daudé]

On 10/10/21 19:43, Richard Henderson wrote:
> While the host may prefer to treat 32-bit addresses as signed,
> there are edge cases of guests that cannot be implemented with
> addresses 0x7fff_ffff and 0x8000_0000 being non-consecutive.
> 
> Therefore, default to guest_base_signed_addr32 false, and allow
> probe_guest_base to determine whether it is possible to set it
> to true.  A tcg backend which sets TCG_TARGET_SIGNED_ADDR32 will
> have to cope with either setting for user-only.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/exec/cpu-all.h  | 16 ++++++++++++++++
>  include/exec/cpu_ldst.h |  3 ++-
>  bsd-user/main.c         |  4 ++++
>  linux-user/main.c       |  3 +++
>  4 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
> index 32cfb634c6..80b5e17329 100644
> --- a/include/exec/cpu-all.h
> +++ b/include/exec/cpu-all.h
> @@ -146,6 +146,7 @@ static inline void tswap64s(uint64_t *s)
>  
>  #if defined(CONFIG_USER_ONLY)
>  #include "exec/user/abitypes.h"
> +#include "tcg-target-sa32.h"

Unrelated but this header could be simplified by moving this
block to a new header such "exec/user/address.h".

>  
>  /* On some host systems the guest address space is reserved on the host.
>   * This allows the guest address space to be offset to a convenient location.
> @@ -154,6 +155,21 @@ extern uintptr_t guest_base;
>  extern bool have_guest_base;
>  extern unsigned long reserved_va;
>  
> +#if TCG_TARGET_SIGNED_ADDR32 && TARGET_LONG_BITS == 32
> +extern bool guest_base_signed_addr32;
> +#else
> +#define guest_base_signed_addr32  false
> +#endif
> +
> +static inline void set_guest_base_signed_addr32(void)
> +{
> +#ifdef guest_base_signed_addr32
> +    qemu_build_not_reached();
> +#else
> +    guest_base_signed_addr32 = true;
> +#endif
> +}
> +
>  /*
>   * Limit the guest addresses as best we can.
>   *

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>