Re: [Qemu-devel] [PATCH 14/17] ppc: Add dummy write to VTB

[Thomas Huth]

On 14.03.2016 17:56, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt <address@hidden>
> 
> The Hypervisor can write it. We don't handle that properly yet but
> at least let's not blow up when it is written.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> ---
>  target-ppc/translate_init.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index 2fac6ea58698..28a9c2e73156 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -300,6 +300,12 @@ static void spr_write_purr(DisasContext *ctx, int gprn, 
> int sprn)
>      /* Temporary placeholder */
>  }
>  
> +__attribute__ ((unused))
> +static void spr_write_vtb(DisasContext *ctx, int gprn, int sprn)
> +{
> +    /* Temporary placeholder */
> +}

Why "__attribute__ ((unused))" here (again)?

>  #endif
>  #endif
>  
> @@ -8089,10 +8095,11 @@ static void gen_spr_power8_ebb(CPUPPCState *env)
>  /* Virtual Time Base */
>  static void gen_spr_vtb(CPUPPCState *env)
>  {
> -    spr_register(env, SPR_VTB, "VTB",
> -                 SPR_NOACCESS, SPR_NOACCESS,
> -                 &spr_read_tbl, SPR_NOACCESS,
> -                 0x00000000);
> +    spr_register_hv(env, SPR_VTB, "VTB",
> +                   SPR_NOACCESS, SPR_NOACCESS,
> +                   &spr_read_tbl, SPR_NOACCESS,
> +                   &spr_read_tbl, spr_write_vtb,
> +                   0x00000000);
>  }

I think it would also be possible to use spr_access_nop() for now
instead of introducing more dummy functions like spr_write_vtb.

 Thomas