Re: [PATCH v2 8/8] target/ppc: 74xx: Set SRRs directly in exception code

[BALATON Zoltan]

On Thu, 27 Jan 2022, Fabiano Rosas wrote:
> The 74xx does not have alternate/hypervisor Save and Restore
> Registers, so we can set SRR0 and SRR1 directly.
>
> Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
> ---
> target/ppc/excp_helper.c | 13 ++-----------
> 1 file changed, 2 insertions(+), 11 deletions(-)
>
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index b7921c0956..4e6bb87b70 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -556,7 +556,6 @@ static void powerpc_excp_74xx(PowerPCCPU *cpu, int excp)
>     CPUState *cs = CPU(cpu);
>     CPUPPCState *env = &cpu->env;
>     target_ulong msr, new_msr, vector;
> -    int srr0, srr1;
>
>     if (excp <= POWERPC_EXCP_NONE || excp >= POWERPC_EXCP_NB) {
>         cpu_abort(cs, "Invalid PowerPC exception %d. Aborting\n", excp);
> @@ -575,10 +574,6 @@ static void powerpc_excp_74xx(PowerPCCPU *cpu, int excp)
>      */
>     new_msr = env->msr & ((target_ulong)1 << MSR_ME);
>
> -    /* target registers */
> -    srr0 = SPR_SRR0;
> -    srr1 = SPR_SRR1;
> -
>     /*
>      * Hypervisor emulation assistance interrupt only exists on server
>      * arch 2.05 server or later.
> @@ -731,10 +726,6 @@ static void powerpc_excp_74xx(PowerPCCPU *cpu, int excp)
>             cpu_abort(cs, "Trying to deliver HV exception (MSR) %d with "
>                       "no HV support\n", excp);
>         }

If we have ho MSR_HVB why is this still here? Shouldn't it have been gone 
in patch 2? Or is this still reachable?

Regards,
BALATON Zoltan

> -        if (srr0 == SPR_HSRR0) {
> -            cpu_abort(cs, "Trying to deliver HV exception (HSRR) %d with "
> -                      "no HV support\n", excp);
> -        }
>     }
>
>     /*
> @@ -746,10 +737,10 @@ static void powerpc_excp_74xx(PowerPCCPU *cpu, int excp)
>     }
>
>     /* Save PC */
> -    env->spr[srr0] = env->nip;
> +    env->spr[SPR_SRR0] = env->nip;
>
>     /* Save MSR */
> -    env->spr[srr1] = msr;
> +    env->spr[SPR_SRR1] = msr;
>
>     powerpc_set_excp_state(cpu, vector, new_msr);
> }