On Wed, 19 Feb 2020, David Gibson wrote:
> The PowerPC 970 CPU was a cut-down POWER4, which had hypervisor capability.
> However, it can be (and often was) strapped into "Apple mode", where the
> hypervisor capabilities were disabled (essentially putting it always in
> hypervisor mode).
>
> That's actually the only mode of the 970 we support in qemu, and we're
> unlikely to change that any time soon.  However, we do have a partial
> implementation of the 970's HID4 register which affects things only
> relevant for hypervisor mode.
>
> That stub is also really ugly, since it attempts to duplicate the effects
> of HID4 by re-encoding it into the LPCR register used in newer CPUs, but
> in a really confusing way.
>
> Just get rid of it.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> Reviewed-by: Cédric Le Goater <clg@kaod.org>
> Reviewed-by: Greg Kurz <groug@kaod.org>
> ---
> target/ppc/mmu-hash64.c         | 28 +---------------------------
> target/ppc/translate_init.inc.c | 17 ++++++-----------
> 2 files changed, 7 insertions(+), 38 deletions(-)
>
> diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> index da8966ccf5..a881876647 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -1091,33 +1091,6 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
>
>     /* Filter out bits */
>     switch (env->mmu_model) {
> -    case POWERPC_MMU_64B: /* 970 */
> -        if (val & 0x40) {
> -            lpcr |= LPCR_LPES0;
> -        }
> -        if (val & 0x8000000000000000ull) {
> -            lpcr |= LPCR_LPES1;
> -        }
> -        if (val & 0x20) {
> -            lpcr |= (0x4ull << LPCR_RMLS_SHIFT);
> -        }
> -        if (val & 0x4000000000000000ull) {
> -            lpcr |= (0x2ull << LPCR_RMLS_SHIFT);
> -        }
> -        if (val & 0x2000000000000000ull) {
> -            lpcr |= (0x1ull << LPCR_RMLS_SHIFT);
> -        }
> -        env->spr[SPR_RMOR] = ((lpcr >> 41) & 0xffffull) << 26;
> -
> -        /*
> -         * XXX We could also write LPID from HID4 here
> -         * but since we don't tag any translation on it
> -         * it doesn't actually matter
> -         *
> -         * XXX For proper emulation of 970 we also need
> -         * to dig HRMOR out of HID5
> -         */
> -        break;
>     case POWERPC_MMU_2_03: /* P5p */
>         lpcr = val & (LPCR_RMLS | LPCR_ILE |
>                       LPCR_LPES0 | LPCR_LPES1 |
> @@ -1154,6 +1127,7 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
>         }
>         break;
>     default:
> +        g_assert_not_reached();
>         ;

Is this empty statement (lone semicolon) still needed now that you've 
added something to this case? Thought it was only there to be able to add 
a label to it so it could be removed now. (Does this count as a double ; 
that a recent patch was trying to fix?)

Regards,
BALATON Zoltan

>     }
>     env->spr[SPR_LPCR] = lpcr;
> diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
> index a0d0eaabf2..d7d4f012b8 100644
> --- a/target/ppc/translate_init.inc.c
> +++ b/target/ppc/translate_init.inc.c
> @@ -7895,25 +7895,20 @@ static void spr_write_lpcr(DisasContext *ctx, int sprn, int gprn)
> {
>     gen_helper_store_lpcr(cpu_env, cpu_gpr[gprn]);
> }
> -
> -static void spr_write_970_hid4(DisasContext *ctx, int sprn, int gprn)
> -{
> -#if defined(TARGET_PPC64)
> -    spr_write_generic(ctx, sprn, gprn);
> -    gen_helper_store_lpcr(cpu_env, cpu_gpr[gprn]);
> -#endif
> -}
> -
> #endif /* !defined(CONFIG_USER_ONLY) */
>
> static void gen_spr_970_lpar(CPUPPCState *env)
> {
> #if !defined(CONFIG_USER_ONLY)
>     /* Logical partitionning */
> -    /* PPC970: HID4 is effectively the LPCR */
> +    /* PPC970: HID4 covers things later controlled by the LPCR and
> +     * RMOR in later CPUs, but with a different encoding.  We only
> +     * support the 970 in "Apple mode" which has all hypervisor
> +     * facilities disabled by strapping, so we can basically just
> +     * ignore it */
>     spr_register(env, SPR_970_HID4, "HID4",
>                  SPR_NOACCESS, SPR_NOACCESS,
> -                 &spr_read_generic, &spr_write_970_hid4,
> +                 &spr_read_generic, &spr_write_generic,
>                  0x00000000);
> #endif
> }
>