Re: [PATCH v2 02/10] ppc: Remove stub of PPC970 HID4 implementation

[Greg Kurz]

On Wed, 8 Jan 2020 12:08:50 +1100
David Gibson <address@hidden> wrote:

> On Tue, Jan 07, 2020 at 06:36:38PM +0100, Greg Kurz wrote:
> > On Tue, 7 Jan 2020 18:32:15 +0100
> > Greg Kurz <address@hidden> wrote:
> > 
> > > On Tue,  7 Jan 2020 15:48:19 +1100
> > > David Gibson <address@hidden> 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).
> > 
> > Isn't it supervisor mode instead of hypervisor mode ?
> 
> No; hypervisor is correct.  If the cpu was always in supervisor mode,
> the boot OS couldn't access the hypervisor privileged registers that
> are needed for basic setup (e.g. SDR1).  "Apple mode" means the cpu
> doesn't have a supervisor mode that _isn't_ hypervisor privileged and
> hence, can't run guests.
> 

Ok, thanks for the clarification.

> > 
> > > > 
> > > > 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 <address@hidden>
> > > > ---
> > > 
> > > Reviewed-by: Greg Kurz <address@hidden>
> > > 
> > > >  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();
> > > >          ;
> > > >      }
> > > >      env->spr[SPR_LPCR] = lpcr;
> > > > diff --git a/target/ppc/translate_init.inc.c 
> > > > b/target/ppc/translate_init.inc.c
> > > > index d33d65dff7..436d0d5a51 100644
> > > > --- a/target/ppc/translate_init.inc.c
> > > > +++ b/target/ppc/translate_init.inc.c
> > > > @@ -7884,25 +7884,20 @@ 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
> > > >  }
> > > 
> > > 
> > 
>

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